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Ok... trying something else. You all gotta give me feedback to what you read...¬†ūüėȬ†otherwise I'll jump all over the place. Let's try¬†this. This is the Weather Prediction Center Extended Forecast Discussion. It give you what they think will happen over the next 3-7 days, so it looks out a little further than just a few days. Let me know what you think.

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Wed Sep 25 2019

Valid 12Z Sat Sep 28 2019 - 12Z Wed Oct 02 2019

  • Much below normal temperatures expected in the West with winter¬†weather possible for the northern Rockies
  • Much above normal temperatures expected in the eastern third of¬†the nation
  • A couple potential rounds of heavy rain expected across the¬†central U.S.

Pattern Overview and Guidance/Uncertainty Assessment:
Guidance continues to show a highly amplified western
trough/eastern ridge pattern whose large scale typically yields
fairly high predictability
.  The relative agreement of
latest/recent GFS-ECMWF runs and their respective means supports
this idea.  Through mid-period the UKMET agreed as well, so the
updated forecast reflected a blend of the 18Z GFS and 12Z
ECMWF/UKMET.  What differences existed were well within typical
error ranges for the forecast time frame.  Even to day 7 Wed the
GFS/ECMWF were sufficiently close to their respective means that a
model/mean blend represented consensus well
.  Late in the period
the greatest uncertainty involved exactly how approaching Pacific
flow (south of a trough/upper low reaching the northeastern
Pacific) will begin to eject the western trough.  By day 7 Wed the
ensemble means provided a centered position with GFS runs faster
and the ECMWF a little slower (leading to the model/mean blend
keeping the trough close to the means).

As for some forecast details, the latest guidance cluster is
consistent with the idea of the western trough containing a
Northwest upper low that may not move much between Sat and Mon or
early Tue.  At the same time eastern ridge aloft amplifies over
the East with the anchoring upper high retrograding as far west as
over or just east of the Lower Mississippi Valley by early Mon.
Shortwave energy ejecting from the western trough should support a
surface wave that emerges from the West and tracks across the
northern Plains/Upper Great Lakes around Sun-Mon before continuing
into Canada.  By next Tue-Wed the front trailing from this wave
and extending to and beyond the central High Plains may decelerate
for a time as it becomes nearly parallel to flow aloft.

Weather Highlights/Threats:
Guidance continues to highlight heavy precipitation potential over
locations from the northern Rockies/High Plains into parts of the
Great Basin.  Expected slow movement of the upper low center over
the interior Northwest should lead to a period of enhanced precip
over terrain favored by southwesterly flow aloft.  Meanwhile
eastern slopes of the northern Rockies will see a period of low
level upslope flow.  Heaviest snow should fall over western
Montana while some lower elevations to the east may see meaningful
snow as well.  Northern California and Pacific northwest rain/high
elevation snow still looks to be lighter and more scattered.
Areas from the Great Basin into the central Rockies may see a
period of relatively stronger winds.

Moisture will spread across the northern Plains as well as the
Midwest/Upper Mississippi Valley/western Great Lakes as low
pressure tracks across the northern tier, with areas of locally
heavy rainfall possible.  Then another episode of heavy rainfall
will be possible from the central Plains northeast into the Great
Lakes around Tue-Wed as the front trailing from the aforementioned
wave may slow down as it becomes aligned with flow aloft.  This
latter event has the potential to produce heavier totals due to
repeat activity/training, plus possible input of moisture
originating from the tropical eastern Pacific--which on the way
toward the region may also play a part in promoting pockets of
enhanced rainfall over or near the southern High Plains.

Easterly flow around the southern side of the strong eastern ridge
aloft should still lead to a slow increase of moisture over
Florida.  The most likely scenario would have Tropical Storm Karen
eventually being steered by this flow, though multi-day trends
have been considerably slower (reaching near the Bahamas by around
day 7 for the past 2-3 days) and the full range of guidance spans
a wide envelope.  Monitor NHC forecasts for the latest information
regarding Karen.

Forecasts continue to show a broad area of the western U.S. into
northern Plains with highs 10-25F below normal during most of the
period--and locally 25-35F below normal over some locations in
Montana.  Morning lows will tend to be 5-15F below normal from Sun
onward, again locally colder in parts of Montana
.  Eastern areas
into the Midwest and central/southern Plains will see much above
normal temperatures with anomalies for highs generally plus
10-20F, and some lows possibly 20-25F above normal during the
first half of next week from the central Plains into Great Lakes.
Expect numerous daily record highs/warm lows during the period.

Rausch

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Sep 26 2019

Valid 12Z Sun Sep 29 2019 - 12Z Thu Oct 03 2019

  • Much below normal temperatures over the West/northern Plains¬†with heavy snow possible in the northern Rockies
  • Much above normal temperatures over the East, extending for a time as far west as parts of the Plains
  • Heavy rainfall potential from the southern High Plains into¬†¬†Great Lakes


Pattern Overview and Guidance/Uncertainty Assessment:

From Sun into Mon the models and ensemble means remain agreeable
and consistent with the forecast of a very amplified pattern
consisting of a western trough containing an upper low over the
Northwest and eastern ridge whose upper high center reaches near
the Lower Mississippi Valley.  The first guidance discrepancy
arises as some combination of ejecting western trough energy and
southern Canada flow propels northern Plains low pressure on Mon
northeast into Canada.  After Tue consensus shows a fairly rapid
flattening of the mean pattern as a northeastern Pacific trough
drops southeast toward the West Coast, ejecting the initial
western trough.  There has been some spread/variability with how
quickly the initial trough departs (though perhaps a little less
than could be the case in such situations) and with details of
height falls reaching the West Coast by next Thu.

Based on guidance through the 12Z-18Z cycles, an operational model
blend represented consensus well for days 3-4 Sun-Mon
.  Even into
day 5 Tue a model blend with a modest introduction of the 18Z
GEFS/12Z ECMWF means provided a reasonable compromise for timing
of the northern Plains into Canada surface low.  The 12Z ECMWF and
12-18Z GFS runs jumped faster than some previous runs and 12Z-00Z
CMC/UKMET runs and the new 00Z GFS is even faster.  Ensemble mean
signals have been mixed as well with the ECMWF mean supporting the
ECMWF/GFS versus the slower CMC/GEFS means.  Over a multi-day time
frame the timing has varied and important upper details are small
enough in scale to have relatively lower predictability--favoring
an intermediate approach.

Over the past couple days the operational models and ensembles
have shown fairly significant spread for specific details of the
northeast Pacific trough dropping toward the West Coast.  The
primary guidance consideration was to phase out the 12Z ECMWF from
the model/ensemble mean blend after day 6 Wed due to its faster
trough arrival versus most other solutions.  The new 00Z
GFS/CMC/GEFS mean maintain support for the trough axis remaining
off the West Coast into Thu.


Weather Highlights/Threats:

The upper low over the Northwest and strong low level easterly
flow north of surface low pressure over the north-central Rockies
will support continued heavy precipitation over the northern
Rockies through the weekend.  The greatest snow totals should be
over higher elevations of western Montana with some snow possibly
extending to somewhat lower elevations to the east or northeast.
The surface low will likely bring areas of locally heavy rainfall
across the extreme northern Plains into the Upper Mississippi
Valley/Upper Great Lakes Sun into Mon.

At the same time flow around the western side of the eastern ridge
aloft should begin to bring rainfall-enhancing moisture from the
tropical eastern Pacific and Mexico into the southern High Plains.
 This flow may persist through midweek, leading to multiple
episodes of locally heavy rainfall over the region.  The
interaction of this moisture and wavy front trailing from the
northern Plains/Canada low will raise the potential for a heavy
rainfall event from the central Plains northeast into the Great
Lakes (centered over Iowa).  The signal for this event has
persisted over the past couple days and the possibility that the
front moves slowly for a day or two would allow for significant
rainfall totals due to training/repeat activity.  To a lesser
degree some moisture should extend into New England.

Deep-layer easterly flow will promote an increase in rain/showers
over Florida.  The flow may ultimately contain some moisture
associated with Tropical Storm Karen, but Karen itself is
currently forecast to weaken slowly to a tropical depression and
then a post-tropical remnant low in the coming days.  Monitor NHC
forecasts for the latest information regarding Karen.

The most extreme temperature anomalies over the lower 48 will
exist from Sun into early next week.  The western U.S. into
northern Plains will see highs 10-25¬ļF below normal with localized
areas in Montana seeing highs at least 30¬ļF below normal
.
 Daily
records for cold highs are most likely on Sun but some are
possible beyond then.  The east will see a broad area of plus
10-20¬ļF anomalies for highs with numerous daily records.
 The
northern Plains low pressure early in the week will also bring a
surge of warmth into parts of the central U.S. with morning lows
particularly warm (plus 20¬ļF or greater anomalies) from the central
Plains into Great Lakes.  As the pattern aloft begins to trend
less amplified expect a gradual moderation of chilly western
U.S./northern Plains temperatures while warm to hot readings
become more confined to the East--with some record highs/warm lows
continuing to be possible into Wed-Thu.

Rausch

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Fri Sep 27 2019

Valid 12Z Mon Sep 30 2019 - 12Z Fri Oct 04 2019

  • Heavy rainfall potential from the southern High Plains into Great Lakes early to middle of next week
  • Anomalous warmth continues over the central to eastern U.S. while very chilly conditions remain across the northern and northwestern U.S

Pattern Overview and Guidance/Uncertainty Assessment:

A highly amplified large-scale pattern across the U.S. will appear
to become more zonal by late next week.  However, a cold trough
over the Northwest while an anomalously strong upper ridge over
the Southeast will likely to remain persistent through the medium
range.  Meanwhile, a wavy front is forecast to gradually move
across the central and eastern U.S.  Ensemble consensus remains
quite good, while deterministic guidance has increased its speed
of ejecting energy from the western trough eastward across the
north central U.S. toward the Northeast.  The Canadian model
appears to eject too much energy farther north into Ontario,
Canada by midweek. Therefore, the WPC grids were derived using a
blend of the 12Z ECMWF and 18Z GFS with a small percentage of
their ensemble means for days 3-4 (Mon-Tue).  The 12Z NAEFS was
introduced into the blend by day 5, with increasing weights
through day 7 together with the 12Z EC mean and 18Z GEFS.
Confidence is good based on ensembles that another vigorous
shortwave should drop into the Pacific Northwest for the latter
part of next week, reinforcing the amplitude of the upper trough
over the area, while a less anomalous ridge remains over the
Southeast.


Weather Highlights/Threats:

With the guidance trending faster eastward ejection of the energy
from the western trough, an early end to the heavy precipitation
is indicated over the northern Rockies by Monday as the main
surface cyclone moves into the northern Plains.  The trailing cold
front is expected to move across the Plains relatively slowly as
it assumes a more zonal orientation through the end of next week.
Meanwhile, flow around the western side of the eastern ridge aloft
should begin to bring rainfall-enhancing moisture from the
tropical eastern Pacific and Mexico into the southern High Plains.
The interaction of this moisture with the wavy front will raise
the potential for a heavy rainfall event from the central Plains
northeast into the Great Lakes (centered over Iowa).  The signal
for this event has persisted over the past couple days and the
possibility that the front moves slowly for a day or two would
allow for significant rainfall totals due to training/repeat
activity.  To a lesser degree some moisture should extend into New
England.

Deep-layer easterly flow, associated will the decaying Tropical
Storm Karen, will promote an increase in rain/showers over
Florida.  Please monitor NHC forecasts for the latest information
regarding Karen.

The most extreme temperature anomalies over the U.S. mainland will
exist through early next week.  The western U.S. into northern
Plains will see highs 10-25F below normal with localized areas in
Montana seeing highs at least 30F below normal.
 Daily records for
cold highs are most likely on Sun but some are possible beyond
then.  The east will see a broad area of plus 10-20F anomalies for
highs with numerous daily records.  The northern Plains low
pressure early in the week will also bring a surge of warmth into
parts of the central U.S. with morning lows particularly warm
(plus 20F or greater anomalies) from the central Plains into Great
Lakes.  As the pattern aloft begins to trend less amplified,
expect a gradual moderation of chilly western U.S./northern Plains
temperatures.  However, record highs/warm lows remain a distinct
possibility over the southeastern U.S. through late next week.

Kong/Rausch

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Sep 28 2019

Valid 12Z Tue Oct 01 2019 - 12Z Sat Oct 05 2019

  • Heavy rainfall potential from the central Plains to the lower¬†Great Lakes in the middle of next week
  • Anomalous warmth to persist over the central to eastern U.S.,¬†while very chilly conditions moderate somewhat in the northern and¬†northwestern states

Pattern Overview and Guidance/Uncertainty Assessment:

Model guidance this evening continues to indicate a deep upper low
over the northwestern U.S. will eject eastward toward the Great
Lakes during the medium-range period.  This will lead to a more
zonal pattern across the northern tier states by the end of next
week as a strong upper ridge gradually weakens over the Southeast.

 Meanwhile, another upper trough moving toward British Columbia
will likely amplify when it reaches the Pacific Northwest late
next week.  A wavy front is forecast to gradually move across the
central and eastern U.S. next week, with a swath of heavy
precipitation possible from the central Plains to the lower Great
Lakes in the middle of the week.

Ensemble consensus remains quite good through the medium-range
period.  The 18Z GFS shows the formation of an anomalous low
across the Northeast toward the end of next week.  This low was
not supported by other deterministic solutions nor the ensemble
means.  Nevertheless, ensemble solutions suggest the formation of
a frontal wave somewhere in the vicinity of northern Mid-Atlantic
to the Northeast late next week. This is reflected on the Day 7
prognostic chart.  The WPC grid package is comprised of a
consensus of the 12Z ECWMF, and the 18Z GFS through day 5, with a
higher percentage given to the 12Z EC mean.  Increasing weight was
given to the 12Z EC mean beyond day 5, mixing in with some 18Z
GEFS and 12Z NAEFS.

Links

 

Weather Highlights/Threats:

A wavy trailing front will become the focus for precipitation
across the central Plains to the lower Great Lakes by midweek as
the upper-level flow becomes more zonal. Flow around the western
periphery of the strong ridge over the southeastern U.S. will draw
tropical moisture from the eastern Pacific Ocean northward and
then interact with the frontal boundary.  Potential exists for a
few inches of rain along a band across the central Plains to the
lower Great Lakes during the middle of the week, with the
possibility of flash flooding.

Deep-layer easterly flow, associated will the decaying Tropical
Storm Karen, will promote an increase in showers and thunderstorms
over Florida.  Please monitor NHC forecasts for the latest
information regarding Karen.

Very chilly conditions over the western U.S. into Northern Plains
are expected to moderate somewhat by early next week.  On the
other hand, many locations from the Gulf Coast to New England will
be averaging 10-20¬ļF warmer with numerous daily records expected be
broken.

Kong
 

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EDT Mon Sep 30 2019

Valid 12Z Thu Oct 03 2019 - 12Z Mon Oct 07 2019

  • Heavy rain threat diminishes over the central Plains late this week but could return by next Sunday into Monday
  • Record warmth continues for the Southeast into Thursday

Overview and Guidance/Uncertainty Assessment:

Relatively zonal/progressive flow is expected to be in place
across the CONUS to start the medium range period as an upper
trough initially across the Rockies lifts out into the central
U.S.  The heavy rain threat should be diminishing along a wavy
surface front across the central Plains.  Meanwhile, a less
vigorous upper trough is forecast to move through the Pacific
Northwest and the northern Rockies late this week before moving
into the Plains by this weekend and into next Monday.  There are
some indications for heavy rain to develop over the central Plains
these couple of days as a low pressure system could form.

Global models show fairly good agreement on the synoptic pattern
evolution across the U.S. through Day 5 (Sat).  There is a trend
toward a more robust development of a frontal wave over the
Northeast on Thursday and Friday, especially the GFS.  By Sunday
and Monday, potential exists for another frontal wave to develop
in the Midwest.  Therefore, more of the ensemble means are used to
handle the uncertainty for this system.  The WPC medium range
forecast was a general consensus of the 12Z ECMWF and the 18Z GFS
together with their ensemble means.  Only a small percentage of
the 18Z GFS is used for days 6 and 7 since the frontal wave
appears to be too strong.


Weather Highlights/Threats:

The heavy rain threat near a frontal boundary across the central
Plains should begin to diminish on Thursday as the main dynamics
of the system shifts further northeast into New England ahead of a
developing frontal wave.  Localized heavy rain is possible across
portions of New England on Thursday into early on Friday as the
frontal wave could strengthen before it moves offshore.
Meanwhile, a vigorous upper trough is expected to bring scattered
mixed precipitation across the northern Rockies on Friday.  By the
weekend, the upper trough should begin to inject moisture from the
Gulf and increase the threat of heavy over the central Plains
ahead of a frontal system.

Record warmth over the Southeast is expected to continue into
Thursday before a gradual cooling trend sets in.  Overall,
temperatures will become less extreme across the country as we
head toward the weekend.

Meanwhile,  deep-layer easterly flow will bring an influx of
tropical moisture across southern Florida and into the Gulf of
Mexico this week north of a tropical low.

Kong

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Tue Oct 01 2019

Valid 12Z Fri Oct 04 2019 - 12Z Tue Oct 08 2019

  • Central U.S. heavy rain threat diminishes late this week but¬†could return/extend eastward by the weekend and early next week
  • Record warmth continues for the Southeast into Thursday

Overview and Guidance/Uncertainty Assessment:

A less amplified and more seasonable mean flow aloft is expected
to begin the medium-range period before the pattern possibly
becoming more amplified again by early next week.  Models have
come into better agreement with an intensifying low pressure wave
to move quickly off to the east of New England on Friday.  The
trailing cold front will bring an end to the record heat over the
eastern U.S.
 Meanwhile, an upper-level trough is forecast to
progress steadily through the western U.S. and should reach the
Plains during the weekend.  Model guidance appears to indicate a
trend toward a more amplified broad scale pattern, with larger
than normal uncertainty regarding the subsequent evolution of this
trough as it heads toward the East Coast early next week.

The WPC forecast grids were derived mostly from a blend of the 18Z
GFS and the 12Z ECMWF, with more weights given to the ECMWF.  Some
12Z UKMET and 12Z Canadian solutions were also used.  It was noted
that the ECMWF, UKMET, and Canadian models showed a more
amplified/sharper configuration near the base of the upper trough
over the western U.S. which was different from the less amplified
version indicated by the GFS. The most amplified solution, as
shown by the 12Z ECMWF, led to cyclogenesis over the southeastern
U.S. by next Tuesday.  This scenario was not yet supported by its
ensemble mean however.
 Therefore, a more conservative approach
was used to handle the uncertainty by blending the 12Z EC mean,
18Z GEFS, and some 12Z NAEFS for days 6 and 7. This yielded good
continuity with the previous WPC medium range package.


Weather Highlights/Threats:

The low pressure system moving pass New England Thursday night
will bring focused rainfall to areas near/north of the low track.
Rainfall along the trailing front will diminish except for some
activity persisting over the southern Rockies/High Plains where
the front will stall for a day or so.  The system emerging from
the West and into the Plains should bring scattered rain/high
elevation snow to northern parts of the West late this week and
then support some areas of locally moderate to heavy rain over the
central U.S. by this weekend.  The forecast becomes more uncertain
by Sun-Mon given poor agreement regarding upper level flow details
that will determine frontal timing/waviness and how much moisture
may flow northward from the Gulf of Mexico.  At the very least
there is the potential for some areas to see significant rainfall
but at this time confidence is very low for specifics.  Locations
along the eastern half of the Gulf Coast may also see periods of
enhanced rainfall with moisture around the periphery of Gulf of
Mexico low pressure and near a potential upper level weakness/low.


Record warmth over the eastern and southeastern U.S. should
largely come to an end on Friday behind a cold front
.  Meanwhile,
expect unseasonably cool readings over the Northwest (10-20F below
normal) to persist late this week and then trend closer to normal
over the Pacific Northwest followed by the northern Rockies.

Kong/Rausch

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Wed Oct 02 2019

Valid 12Z Sat Oct 05 2019 - 12Z Wed Oct 09 2019

Overview and model uncertainty assessment:

Global models are in very good agreement on the speed and
evolution of the upper-level trough forecast to move across the
northern tier states during the weekend.  By early next week,
models appear to show an increasing potential for the pattern to
become more amplified, resulting in higher uncertainty in the
forecasts from early to the middle of next week.  One area to
monitor will be in the eastern U.S. where both the GFS and ECMWF
have indicated cyclogenesis in some previous runs.
 However, there
continues to be considerable run-to-run variability regarding this
potential system. In addition, their ensemble means still do not
indicate any signs of an East Coast cyclone.

Another area of uncertainty will be over the Pacific Northwest
from early to the middle of next week as the next upper trough
arrives.  The ECMWF has been showing the tendency for an upper low
to form offshore while the GFS is much more progressive in
bringing the trough onshore.  The WPC forecast package was
primarily derived from a composite blend of the 18 UTC GFS and the
12 UTC ECMWF, with increasing emphasis on their ensemble means for
day 6 and 7 to handle the increasing uncertainty.  This yielded
generally good continuity with the previous WPC forecast package,
but with a faster progression of the upper trough and surface cold
fronts across the Pacific Northwest toward the middle of next week.


Weather Pattern Highlights/Threats:

An upper trough working its way into the northern Plains will
bring a round of showers across the Midwest and Great Lakes during
the weekend.  As the trailing cold front forecast to slow down,
there is an increasing chance for precipitation to linger across
the southern Plains into the Tennessee Valley during the weekend.
There is some potential for heavy rain to train across the
Tennessee Valley as well.
 General rain is forecast to move
through the East Coast early next week and off the coast by
Wednesday.

Temperatures across the country will be less extreme by the
weekend and lasting through midweek next week with readings
staying within 12 degrees from normal.  The western U.S. upper
trough will bring scattered rain/high elevation snow to the
Pacific Northwest and northern Rockies through midweek next week.
Meanwhile, tropical moisture north of a tropical low will bring a
good chance of thunderstorms across Florida.  The heaviest rains
are expected to stay in the Gulf of Mexico through midweek next
week.

Kong

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
306 AM EDT Thu Oct 03 2019

Valid 12Z Sun Oct 06 2019 - 12Z Thu Oct 10 2019

Overview and model uncertainty assessment:

Global deterministic guidance this evening shows fairly good
agreement on the synoptic pattern beginning on Sunday with a
trough moving into the eastern U.S. and a ridge moving across the
northern Rockies.
 The ECMWF continues to depict a more amplified
pattern than other guidance, which leads to lower predictability
across the U.S. toward the middle of next week.  On the other
hand, the GFS has been showing more run-to-run consistency with
the next upper trough moving into the northwestern U.S. next
Tuesday and Wednesday.  The Canadian model agrees with this
scenario.  This would bring a cold front fairly quickly across the
Pacific Northwest and then into the Plains during midweek next
week.

The WPC forecast package was primarily derived from a composite
blend of the 18Z GFS and the 12Z ECMWF, together with a smaller
percentage from the 12Z Canadian model.  More of the ensemble
means from the 18Z GEFS and the 12Z EC mean were incorporated for
Days 5 to 7 with higher emphasis on the 18Z GEFS due to its better
run-to-run consistency on handling the upper trough over the
western U.S.


Weather Pattern Highlights/Threats:

A fairly strong low pressure system should be tracking north of
the Great Lakes on Sunday, bringing a reinforcing shot a cool air
from Canada into the region with blustery winds.  The trailing
cold front is expected to slow down slightly as it heads toward
the Appalachians with some locally heavy rainfall possible later
on Sunday.
 More general rainfall is expected for the East Coast
on Monday before the front moves off the coast on Tuesday.

Over the Pacific Northwest, precipitation associated with the next
upper trough is expected to arrive on Tuesday.  Scattered higher
elevation snowfall is expected to reach the northern Rockies
Tuesday night to Wednesday.  The cold air behind the upper trough
will drive a cold front quickly into the Plains by Thursday.
Scattered showers are expected to form ahead of the front over the
central Plains on Thursday.

Temperatures across the country will be less extreme by next week.
However, the reinforcing cold air behind the upper trough could
drop temperatures to 20 degrees below normal over the northern
Rockies on Wednesday.

Kong

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 AM EDT Fri Oct 04 2019

Valid 12Z Mon Oct 07 2019 - 12Z Fri Oct 11 2019

  • Another round of cold/snow for portions of Montana next week

Overview:
Troughing will exit the Northeast but enter the Pacific Northwest
early next week as a fairly amplified but progressive flow pattern
continues. Western troughing will push through the central states
next Thu/Fri with much below average temperatures in its wake.


Guidance/Uncertainty Assessment:
The 12Z/18Z GFS and 12Z ECMWF offered reasonable clustering near
their ensemble means and each other such that a blend sufficed
through the period. Typical differences within expected errors for
3-7 day lead times suggested at least average confidence. By later
next week, the ECMWF and its ensemble members were generally
quicker with the central CONUS trough than the 18Z GFS/GEFS but
there was quite a bit of east-west spread by next Fri depending on
the wavelength amplitude of the member--the slower members (with a
deeper trough or closed low lingering in the West) were generally
slower downstream with another closed low near the New England
coast (like the 12Z Canadian). For now, GFS/ECMWF/ensemble
consensus was progressive enough to keep the surface front moving
through the week.


Weather Highlights/Threats:
Cold front nearing the East Coast will provide a focus for locally
modest to heavy rainfall from the central Appalachians into the
Northeast Monday. This rainfall will be beneficial over areas
currently experiencing drought of varying intensity.
Brief warm-up
(70s on the coastal plain, 60s inland) will be replaced by near
average temperatures for the rest of the week in much of the East.
By Tue-Thu the front should settle over the Florida Peninsula and
possibly lead to some rainfall enhancement in its vicinity.

The upper trough dropping southeastward from the Gulf of Alaska
will bring a period of rain and initially higher elevation snow to
the Northwest during the first half of next week with highest
totals over favored westward-facing terrain. Winter Weather
Outlook snowfall probabilities exceed 70% (> 2-3" snow) over
higher elevations on Tuesday in western Montana around Glacier
Park. The cold air behind the leading surface front will progress
southward and eastward which will lower snow levels toward or into
the valley locations of the rest of Montana
. High temperatures are
likely to be at least 10-20¬ļ F below average over the northern
Rockies/Plains on Wed and over much of the northern-central Plains
by Thu. This will spread southward to Texas and eastward to the
Mississippi Valley by Friday but perhaps with less intensity.
Rainfall will expand and perhaps become locally heavy over the
mid-Mississippi Valley late in the period depending on moisture
inflow from the Gulf.

Fracasso

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
245 AM EDT Sun Oct 06 2019

Valid 12Z Wed Oct 09 2019 - 12Z Sun Oct 13 2019

  • Another round of cold/snow for the Northern Rockies/Plains next¬†Wed/Thu

Overview:

A positive height anomaly near Labrador/northeastern Quebec will
favor deepening troughing in the western to central states and
increased precipitation for the Mississippi Valley. Western
Atlantic ridging is forecast to compress into the subtropics,
allowing a cutoff upper low to lurk just offshore New England.


Guidance/Uncertainty Assessment:

A blend of the 12Z ECMWF/ECMWF ensemble mean and 18Z GEFS mean
offered a reasonable starting point to the forecast through the
period. The 12Z/18Z GFS's were quicker with the timing of the
western trough as it progressed onto the Plains, against the
multi-day trends and the vast majority of the ensembles. The 12Z
Canadian/UKMET showed a similar slower timing comparable to the
ECMWF. Off the New England coast, the 12Z ECMWF was on the
southern third of the ensemble spread with the potentially
subtropical system while the GFS/Canadian were much farther north.
Preferred an ensemble mean consensus with a weight toward the
ECMWF ensemble mean by next Sat/Sun which was slower to lift the
system northward than the 18Z GEFS mean.


Weather Highlights/Threats:

Strong cold front will push out of the Northern Rockies on
Wednesday which will drag down well below average temperatures
through the region. Record cold is likely for many areas in its
wake for both lows and highs (record cold max temperatures) as
readings may be 20-40 deg F below average
. Cooler air will spread
southward to Texas and eastward to the mid-Mississippi Valley by
Friday but with less intensity. Still, a large area of the CONUS
will see temperatures below average by about 5-15 deg F. The
exception will be east and south of the front, mainly from the
Appalachians eastward and into the Southeast/Florida until the
front passes.

Along with colder temperatures, modest accumulating snowfall is
likely for parts of the Northern Rockies and eventually the
Northern Plains and Upper Midwest
. Ahead of the cold front,
rainfall will expand and offers a risk to become locally heavy
from the south-central Plains to the mid-MS Valley/Midwest later
in the period with moisture inflow return from the Gulf. Rain
threat in general will decrease farther east as the system lifts
into Canada.

The low off the New England coast will bring a threat for locally
heavy rainfall to at least parts of coastal New England next week,
but this is dependent on how close the low tracks to the coast.
NHC is also monitoring this system for potential tropical or
subtropical development. Regardless, stiff easterly onshore flow
will be prevalent through southern New England into the coastal
Mid-Atlantic around its circulation.

Fracasso

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1202 AM EDT Mon Oct 07 2019

Valid 12Z Thu Oct 10 2019 - 12Z Mon Oct 14 2019

  • N-Central Rockies to Northern Plains/Upper Midwest Snow Threat


Guidance/Uncertainty Assessment:

The WPC medium range forecast suite was mainly derived from a
composite blend of well cluster guidance from the latest
GFS/ECMWF/UKMET/Canadian, GEFS/ECMWF ensemble means, and the
National Blend of Models. This forecast plan maintains great WPC
continuity in an active weather pattern with above normal forecast
predictability.


Weather Highlights/Threats:

A strong cold front will dig through the western and central U.S.
into Thu/Fri to bring well below average temperatures through the
region. Some record values may be reached. Cooler air will tend to
moderate and spread across the eastern states over the weekend.

Along with colder temperatures, wrapback moisture and upslope flow
supports some heavy snow threat from the Rockies to the Upper
Midwest with upper closed low and surface frontal low track and
development. Ahead of the cold front, rainfall will expand and
offer a risk of locally heavy rainfall from the s-central Plains
to the mid-MS Valley/Midwest in a region of enhanced moisture
inflow return from the Gulf of Mexico. The rain threat in general
will decrease farther east as the system lifts into Canada.

Downstream, an organized coastal low off the Mid-Atlantic and New
England will meanwhile offer a significant maritime threat and
some coastal rainfall, dependent on how close the low tracks to
the coast. NHC is also monitoring this system for potential
subtropical development. Regardless, stiff easterly onshore flow
will be prevalent through southern New England into the coastal
Mid-Atlantic around its circulation.

Schichtel

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How high is the confidence that north central Wisconsin will see snow this coming weekend October 12-13?

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9 hours ago, Mbruce said:

How high is the confidence that north central Wisconsin will see snow this coming weekend October 12-13?

Pretty good chance to see 2-4" across central Wisconsin, the heavier snow will fall across Minnesota. The GFS is the heaviest, then the Canadian, then the Euro. Much colder temps coming in though

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Tue Oct 08 2019

Valid 12Z Fri Oct 11 2019 - 12Z Tue Oct 15 2019

  • Record cold to gradually relent in the Central Rockies to¬†Northern Plains/Upper Midwest

Pattern Overview and Guidance/Uncertainty Assessment:

An anonymously deep upper low will very slowly lift through the
Upper Midwest/western Great Lakes through the weekend. Near the
east coast, a potential subtropical system is forecast to track
close to southeastern New England (near the 40/70 benchmark). The
National Hurricane Center is monitoring this area for development.
Please reference their outlooks for more information.

The models and ensembles were in generally good/great agreement on
the synoptic pattern with typical timing differences in the
west/central CONUS--GFS generally quicker and ECMWF generally
slower with the UKMET/Canadian in between
. A blended solution was
preferred given the deterministic-subset cluster well within the
multi-center ensemble cluster. Off the east coast, models were
still having trouble resolving the track/intensity and even
structure of the hybrid system through the period. Preferred the
slower/western solutions given the transient Rex block pattern and
separation from the upstream closed/cutoff low which should favor
a system west of 70W. Agreement among the 12Z ECMWF/UKMET/Canadian
with the 12Z ECMWF ensemble mean was convincingly strong.
Ultimately, as the whole pattern unwinds, the Atlantic system will
be pushed farther out to sea as the cold front reaches the east
coast around Sunday.


Weather Highlights/Threats:

Amplified pattern will bring record cold to the west and central
states that will moderate after Friday. Still, temperatures 20-40
degrees below average on Friday should still be below average by
about 10-20 degrees by next Tuesday over the Dakotas. Milder than
average temperatures will precede the cold front across the
eastern states and the South and will stay near to above average
along the Gulf Coast.

Upper Midwest system will continue to bring wind/snow and
pre-frontal/lower-latitude rain to the region Friday.
Precipitation will wind down over the weekend but will continue to
wrap around the surface low as it moves into western Ontario. Over
New England and the coastal Mid-Atlantic, models show large spread
in rainfall amounts depending on the proximity and strength of the
ocean system. For now, took a modest approach given the
uncertainty with 1-1.50" from 12Z Fri onward over eastern MA
diminishing to near zero along/west of I-87.

In the Pacific Northwest, a cold front will push through the area
on Saturday with only light rain and mountain snow Fri/Sat west of
the Cascades that will spread into northern Idaho and northwestern
Montana next Sun/Mon. By then, Gulf moisture may begin to spread
northward as the tail-end of the stationary front may lift back
northward ahead of the western front moving through the Plains.

Fracasso

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
253 AM EDT Wed Oct 09 2019

Valid 12Z Sat Oct 12 2019 - 12Z Wed Oct 16 2019

  • Pattern Overview and Guidance/Uncertainty Assessment

An anomalously deep upper low over northern Minnesota Saturday will
slowly weaken and drift northeastward toward Hudson Bay through
the period. Pacific flow will bring one shortwave to the Pacific
Northwest by the start of the weekend and then the central U.S.
early next week, followed by another shortwave that could approach
the Northwest Tue/Wed. The potential subtropical system just off
the East Coast on Saturday is forecast to move away from New
England Sunday. The National Hurricane Center is monitoring this
area for development. Please reference their outlooks for more
information.

Overall a model/ensemble blend sufficed through the forecast
period with a majority weight to the 12Z ECMWF and its ensemble
mean next Tue/Wed
. GFS runs appeared a bit too quick relative to
the multi-center ensemble spread though recent trends have been a
bit quicker.


Weather Highlights/Threats:

Wrap-around precipitation will wind down across the Upper
Midwest/Great Lakes this weekend but the tail end of the front
will linger across the Southeast.
This will likely spur an
increase in rainfall as the western system organizes in the Plains
by Tuesday. This will be the focus for the potentially heaviest
rainfall through the medium range. Over the eastern Pacific, a
potential tropical system may spread some moisture across northern
Mexico into west Texas but this remains uncertain given the spread
in its track.

Record cold temperatures on Saturday will slowly moderate but
remain much colder than average over the Dakotas and
western/central Great Lakes. Above average temperatures will
precede the cold front in the east on Saturday with modestly above
normal readings persisting over the Southeast through early next
week.

Fracasso

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
242 AM EDT Fri Oct 11 2019

Valid 12Z Mon Oct 14 2019 - 12Z Fri Oct 18 2019

 

Pattern Overview and Guidance/Uncertainty Assessment:


A relatively amplified and progressive pattern will be in place
across the CONUS during the extended period. A deep upper-level
low initially in place just north of the Great Lakes on Mon is
forecast to lift northward across eastern Canada while a cold
front sweeps across the Mid-Atlantic/Northeast. Meanwhile,
shortwave energy crossing the Great Basin/Rockies on Mon and the
central U.S. on Tue is forecast to amplify across the Great Lakes
and eastern U.S. Wed/Thu, moving a relatively strong cold front
off the Eastern Seaboard. The pattern will become much more
unsettled across the Northwest by the middle of next week as a
series of shortwaves/frontal systems approach the region in rapid
succession.

The WPC medium range forecast was based initially on a multi-model
deterministic blend (including the 12Z ECMWF/UKMET/18Z GFS) on
days 3-4 (Mon-Tue). Starting on day 5 (Wed), the GFS was removed
from the blend, as it become significantly faster than the
model/ensemble consensus to lower heights across the Pacific
Northwest and farther inland. The differences only increased later
in the period, with the GFS developing a deep closed upper-level
low across the north central U.S. by days 6-7 (Thu-Fri), while the
ECMWF along with most ECENS and CMCE ensemble members keep broad
anticyclonic flow across the central U.S., and more amplified
troughing along the West Coast. Thus, the forecast during days 5-7
showed gradually increasing weight on the ECENS/NAEFS ensemble
means, with some continued weight on the ECMWF through the end of
the forecast period given a solution that fit reasonably well
within the ensemble consensus.


Weather Highlights/Threats:

A weakening frontal boundary forecast to linger from the lower
Mississippi Valley to the Southeast days 3-4 is expected to
produce widespread showers and thunderstorms, with heavy rain
possible. Model consensus suggests that 2-3 inches of rain may be

possible across portions of these areas Mon-Tue. Farther north,
low pressure expected to move from the mid-Mississippi Valley on
Tue to the Ohio Valley/Northeast Wed/Thu is expected to gradually
draw in deeper moisture, and widespread moderate to locally heavy
rain is forecast across the Northeast Wed into Thu. Meanwhile,
precipitation is expected to gradually increase across the Pacific
Northwest starting next Tue and continuing through the end of the
week as multiple shortwaves/frontal systems affect the region.
Snow-levels are forecast to be relatively high initially, but
should begin to fall by later in the week as lower heights begin
to press inland. Regardless, heavy precipitation is expected to
become widespread across the coastal ranges of the Northwest as
well as the Cascades by later in the week, with multi-inch liquid
equivalents possible.

Temperatures are forecast to initially be well below average
across the north central U.S. in the wake of this weekend's winter
storm. Highs are forecast to be 15-25 deg F below average across
portions of the northern Plains and Upper Midwest Mon-Wed, before
temperatures moderate later in the week. Cooler temperatures are
forecast to spread into the eastern half of the nation by the
middle to end of next week as Canadian high pressure overspreads
the region behind the cold front. High temperatures 5 to 15 deg
below average are forecast across a large area from the
Mississippi River to the Eastern Seaboard.


Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
203 AM EDT Sat Oct 12 2019

Valid 12Z Tue Oct 15 2019 - 12Z Sat Oct 19 2019

Pattern Overview and Guidance/Uncertainty Assessment:


A relatively amplified and progressive pattern will be in place
across the CONUS during the extended period. A shortwave crossing
the northern Plains/Midwest on Tue and the Great Lakes/Northeast
Wed/Thu is forecast to gradually amplify, with a closed upper low
developing across New England by Wed night/Thu morning. At the
surface, a low pressure system and surface frontal system are
forecast to sweep across the eastern half of the nation. Formation
of a new low is expected across the Mid-Atlantic region on Wed,
which is forecast to intensity into a relatively deep cyclone
along the New England coast Wed night/Thu as the upper low
intensifies. Farther west, an intense Pacific upper-level jet is
forecast to reach the Northwest along with a train of shortwaves
starting Wed night, which should quickly lower heights across the
Northwest and eventually the northern Rockies as the series of
systems moves inland. By the end of the forecast period (day
7/Sat), models show quite a bit of spread, but there is some
consensus that the primary trough axis should be centered across
the Rockies with a rapid succession of energy ejecting eastward
across the central U.S.

The 12Z ECMWF/UKMET were heavily used in the forecast during days
3-5 (Tue-Thu). Additionally, the GEFS mean was preferred over the
GFS as the mean was not quite as fast as the operational run to
lower heights farther inland across the Northwest/northern
Rockies. There has been a trend toward faster progression of
energy inland compared to this time last night, but the GFS
remains on the fast side of the model/ensemble spread and was not
preferred at this time. Later in the forecast period model spread
and run-to-run variability increases significantly. The evolution
of shortwave energy across the central U.S./Canada, as well as the
amplitude of additional shortwave energy reaching the West Coast,
during this time frame, are very much in question. Confidence in
the specifics of the forecast by days 6-7 is quite low, especially
across the western and central U.S. A blend of the ECENS/GEFS
ensemble means was primarily used for the day 6-7 forecast to
accommodate the lack of confidence in the specifics.


Weather Highlights/Threats:

A weakening/stalled frontal boundary lingering over the Lower
Mississippi Valley to Southeast on Tue will be the focus for
widespread showers and thunderstorms. Model consensus suggests
that 2-3 inches of rain are possible across portions of these

areas. As the area of low pressure develops mid-week over the
Great Lakes and moves into the Northeast U.S., deeper moisture
will be pulled northward, resulting in widespread rainfall, some
of which could be locally heavy. Meanwhile, precipitation is
expected to gradually increase across the Pacific Northwest
starting Tue and continuing through the the week as multiple
shortwaves/frontal systems affect the region. Snow-levels are
forecast to gradually fall through the week as lower heights begin
to press inland. Heavy precipitation is expected to become
widespread across the coastal ranges of the Northwest as well as
the Cascades by later in the week, with multi-inch liquid
equivalents possible. By late next week, moisture return across
the central U.S. ahead of the western trough could generate
scattered showers across portions of the Mississippi Valley,
meanwhile, a lingering surface front in the Gulf of Mexico may
focus showers along the western/central Gulf Coast.

Temperatures are forecast to initially be well below average
across the north central U.S. in the wake of the current winter
storm. Highs are forecast to be 15-25 deg F below average across
portions of the northern Plains and Upper Midwest Tue-Wed, before
temperatures begin to moderate somewhat later in the week. Cooler
temperatures are forecast to spread into the eastern half of the
nation by the middle next week as Canadian high pressure
overspreads the region behind the cold front. High temperatures 5
to 15 deg below average are forecast across a large area from the
Mississippi River to the Eastern Seaboard Wed-Thu, before

temperatures return to near seasonal norms by next Fri-Sat. Below
average temperatures will spread into the Pacific Northwest and
northern Great Basin by late next week as upper-level heights fall
and the series of frontal systems affect the region.

Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
232 AM EDT Sun Oct 13 2019

Valid 12Z Wed Oct 16 2019 - 12Z Sun Oct 20 2019

Pattern Overview and Guidance/Uncertainty Assessment:

A relatively amplified but progressive pattern will be in place
across the CONUS during the extended period. A trough is forecast
to amplify across the Great Lakes/Northeast Wed/Thu, with a closed
upper-level low expected to develop. At the surface, a low
pressure system and surface frontal system are forecast to cross
the eastern U.S. ahead of the trough
. With the initial surface low
crossing the Great Lakes on Wed, formation of a new surface low is
expected across the Mid-Atlantic region, which is forecast to
quickly intensify as it moves northeastward along the New England
coast Wed night/Thu. Farther west, an intense Pacific upper-level
jet is forecast to reach the Pacific Northwest, along with a train
of shortwave energy, starting Wed night. This should quickly lower
heights across the Northwest and eventually the northern Rockies
as the systems move inland. By Fri, the first significant
shortwave in this series should exit from the Rockies into the
central U.S., pushing a leading cold front into the Plains. Models
show this perhaps being followed by amplification of a more
significant shortwave across the Four Corners region or Rockies by
Sun, poised to move east into the Plains beyond the end of the
forecast period.

The WPC medium range forecast was initially based on a blend of
the 12Z ECMWF/GFS/CMC on days 3-4 (Wed-Thu). The 12Z GFS was
preferred over the 18Z run due to a track closer to the
model/ensemble consensus with the northeastern U.S. coastal low
during this frame. Additionally, a blend of these solutions should
smooth out timing differences with the arrival of the West Coast
trough on Thu. During days 5-7 (Fri-Sun) a gradual trend was shown
toward heavier weighting of ensemble means (ECENS/GEFS). Model
differences were largest with the potential amplification of
shortwave energy across the Four Corners region by next weekend.
In general, the trend in the guidance has been toward a slower and
more amplified system, although the 00Z GFS seemed to back off
that trend (while the CMC continued to trend slower/deeper). Thus,
model spread remains relatively high by next weekend, supporting
the heavier ensemble weighting. Consensus appears much better
across the eastern U.S., where most guidance agrees that
subtropical ridging will build off the Southeast U.S. coast,
lending to greater overall amplification of the pattern and
setting up a broad region of southerly/southwesterly flow across
the Mississippi Valley ahead of the trough.


Weather Highlights/Threats:

Widespread and potentially heavy precipitation is expected across
the Pacific Northwest by mid to late week as the series of
shortwaves and surface fronts move inland. Snow-levels are
forecast to fall as lower height begin to press inland. The
heaviest precipitation is expected to fall across the coastal
ranges as well as the Cascades, with multi-inch liquid equivalents
possible. By next weekend, moisture return across the central U.S.
ahead of the western trough could generate scattered showers and
thunderstorms across portions of the Mississippi Valley.
Meanwhile, a lingering surface front in the Gulf of Mexico may
focus areas of showers and storms along the western/central Gulf
Coast.

Relatively cool conditions are forecast across much of the central
and eastern U.S. Wed into Thu, with highs for many areas 5 to 15
deg F below average. These temperatures should warm by Fri and
into next weekend. Meanwhile, initially above average temperatures
across much of the West (highs 5 to 10 deg above normal) will be
replaced by much cooler conditions as upper troughing moves
inland. Highs are forecast to be 5 to 10 deg below normal across
the Northwest by Thu. By next weekend, colder conditions should
overspread much of the western U.S. as the main upper trough axis
presses inland and amplified, with highs forecast to be as 15 deg
below normal for some areas.

Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
246 AM EDT Mon Oct 14 2019

Valid 12Z Thu Oct 17 2019 - 12Z Mon Oct 21 2019

 

  • Series of storm systems to bring heavy precipitation to the¬†Pacific Northwest later this week

Pattern Overview and Guidance/Uncertainty Assessment:

Amplified and relatively progressive pattern is expected to
continue across the CONUS during the medium range. A deepening
coastal storm is forecast to be ongoing along the New England
coast Thu morning, moving northeast into the Canadian Maritimes by
Thu night/Fri morning, with models now reasonably well-clustered
on the forecast track. Meanwhile, a series of rapidly moving
shortwaves and frontal systems are forecast to affect the
northwestern U.S. from Thu onward, the first of which should be
moving inland across the Rockies on Thu, with systems reaching the
Pacific Northwest spaced approximately 24-36 hours apart through
the rest of the week and into the weekend. The first of the
Pacific shortwaves will move into the central U.S. Fri-Sat,
pushing a cold front across the Plains and the Midwest. By
Sat-Sun, another significant Pacific trough is forecast to quickly
amplify across the Great Basin and Rockies before reaching the
central U.S. by Mon, with a number of model solutions suggesting
development of a closed upper low. Solutions continue to differ on
the timing of this last trough, as well as how far south it digs.

Teleconnections associated with the strongest hemispheric 500 hPa
anomaly centers during the medium range provide somewhat
conflicting guidance. A strong and persistent upper high across
central Russia supports a continuation of relatively progressive
upper flow across the CONUS, but positive height anomalies in the
northeast Pacific support stronger height falls into the
southwestern U.S. (more like the 00Z GFS of 12Z CMC). Given these
considerations a compromise seemed in order, and decided to lean
toward solutions in the middle of the model/ensemble spread.


Based on an evaluation of ensemble members, a blend of the 12Z
ECMWF/GFS/CMC appeared to best represent a consensus for the track
and intensity of the surface low as it moves along the New England
coast and into the Canadian Maritimes Thu/Thu night, and this
blend was followed across the CONUS during days 3-4 (Thu-Fri). The
CMC was dropped from the blend starting on day 5 as it began to
stray from consensus with the central/eastern U.S. shortwave and
was among the deepest/slowest solutions with the strong Pacific
trough across the West on Sun. The forecast during days 5-7
(Sat-Mon) reflected continued use of the 12Z ECMWF/GFS solutions,
with a gradual trend toward greater weighting of ensemble means
(ECENS/NAEFS) through time consistent with increasing guidance
spread.


Weather Highlights/Threats:

Lingering rain is likely across northern New England on Thu as the
deep low pressure system moves along the coast. Sufficient cold
air may be in place for rain with mix with or change to snow at
the highest peaks of the White Mountains. Widespread and
potentially heavy precipitation is expected across the Pacific
Northwest later this week as the series of shortwaves and surface

fronts move inland. Snow-levels are forecast to fall as colder air
and lower height press inland. The heaviest precipitation is
expected to fall across the coastal ranges as well as the
Cascades, with multi-inch liquid equivalents possible. Farther
inland, rain and mountain snows are likely across the northern
Great Basin, northern Rockies, and eventually the central Rockies.
By the weekend, moisture return across the central U.S. ahead of
the western trough could generate showers and thunderstorms across
much of the Mississippi Valley. A weakening warm front may focus
potentially heavy rainfall across portions of the Gulf Coast, from
southeast Texas to the Florida Panhandle. As the warm front along
with deeper moisture drift northward across Sun-Mon, heavy rain is
possible across portion of the lower/mid-Mississippi Valley.

Relatively cool conditions are forecast across the eastern third
of the CONUS on Thu, with highs 5 to 10 deg F below average for

many locations. These areas should warm up by Fri and into the
weekend, with temperatures reaching 5 to 10 deg above normal by
Sun-Mon. Meanwhile, below average temperatures are forecast to
spread across the western U.S. as upper troughing moves inland.
Highs are forecast to be 5 to 10 deg below normal across the
Northwest on Thu. By the weekend, colder conditions should
overspread much of the West as the main upper trough axis moves
inland and amplifies, with highs forecast to be as much as 15 deg
below normal for some areas.

Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
238 AM EDT Tue Oct 15 2019

Valid 12Z Fri Oct 18 2019 - 12Z Tue Oct 22 2019

 

  • Series of storm systems to bring heavy precipitation to the¬†Pacific Northwest
     

Pattern Overview and Guidance/Uncertainty Assessment:

Amplified and relatively progressive pattern is expected to
continue across the CONUS during the medium range. A low pressure
system is forecast to be pulling away from New England Fri
morning, moving northeast into the Canadian Maritimes. Meanwhile,
a series of rapidly moving shortwaves and frontal systems are
forecast to affect the northwestern U.S., spaced approximately

24-36 hours apart into early next week. The first of the Pacific
shortwaves will move into the central U.S. Fri-Sat, pushing a cold
front across the Plains and the Midwest. By Sat-Sun, another
significant Pacific trough is forecast to quickly amplify across
the Great Basin and Rockies before reaching the central U.S. by
Mon, with a number of model solutions suggesting development of a
closed upper low and deep surface cyclone across the Upper
Midwest, which should then lift northward into Ontario on Tue. A
strengthening subtropical ridge off the Southeast U.S. coast early
next week will contribute to a highly amplified flow setup, with a
broad region of moist southerly flow across the Mississippi,
Tennessee, and Ohio Valleys.


The WPC forecast was initially based on a blend of the 12Z
ECMWF/CMC/18Z GFS during days 3-5 (Fri-Sun). These solutions
showed relatively small differences during that time period, and a
blend fit the overall model consensus well. During days 6-7
(Mon-Tue), the forecast was based on a blend of the ECMWF along
with the ECENS and NAEFS ensemble means. The 18Z GFS showed some
significant differences from the ECMWF across the Midwest/Great
Lakes during this time frame, likely due to a less closed
upper-level system causing a leading surface to to move quickly
northeast into the Great Lakes. The ECMWF fit much better within
the center of the model/ensemble spread over the past few runs.


Weather Highlights/Threats:

Widespread and potentially heavy precipitation is expected across
the Pacific Northwest through the weekend as the series of
shortwaves and surface fronts move inland. Snow-levels are
forecast to fall as colder air and lower height press inland. The
heaviest precipitation is expected to fall across the coastal
ranges as well as the Cascades, with multi-inch liquid equivalents
possible. Farther inland, rain and mountain snows are likely
across the northern Great Basin, northern Rockies, and eventually
the central Rockies. As the central U.S. trough amplifies this
weekend into early next week, moisture return from the Gulf of
Mexico will increase. A warm front is expected to focus
potentially heavy rainfall along the immediate Gulf Coast this
weekend, before deeper moisture and widespread
showers/thunderstorms spread north across the Mississippi, Ohio,
and Tennessee Valleys Sun-Mon. Models suggest the potential for
1-2 inches of rain across a large area from the Gulf Coast to the
Ohio Valley, with embedded areas of heavier rainfall.


Relatively cool conditions are forecast across the eastern third
of the CONUS on Fri, with highs 5 to 10 deg F below average for
many locations. These areas should warm up by into the weekend,
with temperatures reaching 5 to 10 deg above normal by Sun-Mon.
Meanwhile, below average temperatures are forecast to spread
across the western U.S. as upper troughing moves inland. High
temperatures 5 to 15 deg below average are forecast to spread from
the Northwest and Great Basin east to the central/northern Rockies
as the main upper trough axis moves inland and amplifies. As the
trough reaches the central U.S. next Mon-Tue, highs may be 5 to 10
deg below average across the central/northern Plains.

Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Wed Oct 16 2019

Valid 12Z Sat Oct 19 2019 - 12Z Wed Oct 23 2019

 

  • Heavy rain and mountain snow expected for portions of the¬†Pacific Northwest


Pattern Overview and Guidance/Uncertainty Assessment:

Amplified and relatively progressive pattern is expected to
continue across the CONUS during the medium range. A series of
rapidly moving shortwaves and frontal systems are forecast to
affect the northwestern U.S., spaced approximately 24-36 hours
apart through early next week. The first of the Pacific shortwaves
will cross the central U.S. Sat, pushing a cold front into the
Great Lakes, Mississippi Valley, and southern Plains. By Sun,
another significant Pacific trough is forecast to quickly amplify
across the Rockies before reaching the central U.S. by Mon. Most
deterministic model solutions suggest development of a closed
upper low and deep surface cyclone across the Upper Midwest/Great
lakes by Mon, which should then lift northward into western
Ontario on Tue. A strengthening subtropical ridge off the
Southeast U.S. coast early next week will contribute to a highly
amplified flow setup, with a broad region of moist southerly flow
across the Mississippi, Tennessee, and Ohio Valleys.


The WPC forecast was initially based on a multi-model
deterministic blend of the 12Z ECMWF/CMC/18Z GFS during days 3-5
(Sat-Mon). Differences among these solutions with respect to
precisely how much and how quickly the upper low deepens across
the Upper Midwest Sun-Mon result in differences on the track and
intensity of the surface low. The CMC differed from consensus a
bit by day 5, closing off the upper low farther south than
consensus, and this solution was thus deemphasized at that time.
Uncertainty increases significantly by days 6-7 (Tue-Wed),
particularly with respect to a building upper ridge off the West
Coast and how it impacts the active train of shortwave energy from
the north Pacific to the northwestern U.S. Models have shown quite
large timing and amplitude variations from run-to-run, which
significantly reduces forecast confidence by that time. A blend of
the 12Z ECENS/NAEFS ensemble means along with a continued minority
component of the deterministic ECMWF was used during this time
period. The ECMWF seemed to best reflect a trend seen among
several deterministic solutions toward faster (and stronger)
arrival of another shortwave in the Northwest on Tue, with further
amplification across the Rockies by Wed. Ensemble means show so
much spread, however, that it is difficult to discern any wave
pattern in the height contours, further emphasizing that forecast
confidence across the western U.S. by the middle of next week is
quite low.



Weather Highlights/Threats:

Widespread and potentially heavy precipitation is expected across
the Pacific Northwest through the weekend as the series of
shortwaves and surface fronts move inland. Significant snows are
possible across the Cascades as well as portions of the northern
Rockies, with heavy rains possible at the lower elevations. As the
central U.S. trough amplifies this weekend into early next week,
moisture return from the Gulf of Mexico will increase. A frontal
boundary and wave of low pressure are expected to focus
potentially heavy rainfall along the immediate Gulf Coast and
perhaps into portions of the Southeast this weekend, before deeper
moisture and widespread showers/thunderstorms spread northward
into the Mississippi, Ohio, and Tennessee Valleys ahead of the

deepening central U.S. low pressure system early next week. By
Mon-Tue as the system moves east, widespread and locally heavy
rains will also be possible across portions of the Northeast.

Below average temperatures are forecast to spread across the
western U.S. as upper troughing moves inland. High temperatures 5
to 15 deg below average are forecast to spread from the Northwest
and Great Basin eastward to the central/northern Rockies as the
main upper trough axis moves inland and amplifies. As the trough
reaches the central U.S. next Mon-Tue, highs may be 5 to 10 deg
below average across the central/northern Plains.

Ryan

 

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
158 AM EDT Thu Oct 17 2019

Valid 12Z Sun Oct 20 2019 - 12Z Thu Oct 24 2019

 

  • Heavy rain and mountain snow expected for portions of the¬†Pacific Northwest


Pattern Overview and Guidance/Uncertainty Assessment:

Amplified and relatively progressive pattern is expected to
continue across the CONUS during the medium range. An area of low
pressure originating in the western Gulf of Mexico is forecast to
across the southeastern U.S. Sun-Mon after merging with a frontal
boundary. Meanwhile, a series of rapidly moving shortwaves and
frontal systems are forecast to affect the northwestern U.S.,
spaced approximately 24-48 hours apart through the middle of next
week. One such Pacific shortwave will cross the Great Lakes on
Sun, with a trailing cold front weakening across the
Mid-Mississippi Valley. Another significant Pacific trough is
forecast to quickly amplify across the Rockies Sun before reaching
the central U.S. on Mon. Most deterministic model solutions
suggest development of a closed upper low and deep surface cyclone
across the Upper Midwest by Mon, which should then lift northward
into the Great Lakes and Ontario on Tue. A strengthening
subtropical ridge off the Southeast U.S. coast early next week
will contribute to a highly amplified flow setup, with a broad
region of moist southerly flow across the Mississippi, Tennessee,

and Ohio Valleys. This will then shift eastward into the
Mid-Atlantic and Northeast by Tue and out to sea on Wed.
Uncertainty increases significantly by Tue-Wed across the Pacific
Northwest and the northeastern Pacific, particularly with respect
to a building upper ridge off the West Coast and how it impacts
the active train of shortwave energy from the north Pacific to the
northwestern U.S. Models have shown quite large timing and
amplitude variations from run-to-run, which significantly reduces
forecast confidence by that time. This uncertainty extends east
into the Rockies and central U.S. by Wed-Thu.

Model differences were quite significant even early in the period
with respect to the low crossing the Southeast and moving. The
UKMET and GFS have consistently shown more interaction with an
additional area of upper-level energy currently across western
Texas, causing the eventual surface low across the Southeast to be
deeper and move faster. Meanwhile, the 12Z ECMWF/CMC showed no or
limited interaction, respectively, with a slower and weaker
surface low across the Southeast. Preferred to lean toward the 12Z
ECMWF/CMC solution until interaction of these feature becomes more
certain, as this also maintains a forecast close to continuity.
These solutions also fit relatively well within the model/ensemble
consensus elsewhere and a 12Z ECMWF/CMC blend was used for the WPC

forecast during days 3-5 (Sun-Tue). The aforementioned blend leans
toward a somewhat deeper and slower solution (relative to the GFS)
with the low pressure system crossing the Midwest/Great Lakes
Mon-Tue. By days 6-7 (Wed-Thu) as uncertainty quickly increased,
preferred to stick relatively close to forecast continuity, which
aligned fairly well with the 12Z CMC. Thus, used a blend of the
12Z CMC along with 12Z ECENS/NAEFS ensemble means by late in the
forecast period.



Weather Highlights/Threats:

Potentially heavy precipitation is expected across the Pacific
Northwest into next week as the series of shortwaves and surface
fronts move inland. Snow levels should rise some as the upper
trough axis shifts to the central/eastern U.S., but some
significant snows will still be possible at the higher elevations
of the Cascades and portions of the northern Rockies. As the
central U.S. trough amplifies this weekend into early next week,
moisture return from the Gulf of Mexico will increase, along with
a chance of severe weather. Advancing frontal boundary and Gulf
low pressure are expected to focus potentially heavy rainfall into
portions of the Southeast this weekend, before deeper moisture and
widespread showers/thunderstorms spread northward into the
Mississippi, Ohio, and Tennessee Valleys ahead of the

strengthening central U.S. low pressure system early next week. By
Mon-Tue as the system moves east, widespread and locally heavy
rains will also be possible across portions of the Northeast.
Maine will be the last to see the rain exit into the Atlantic on
Wednesday.

Below average temperatures are forecast across the western U.S. as
the upper trough moves inland. High temperatures 5 to 15 deg below
average are forecast on Sun from the Northwest and Great Basin
eastward to the central/northern Rockies as the main upper trough
axis moves inland and amplifies. As the trough reaches the central
U.S. next Mon-Tue, highs may be 5 to 10 deg below average across
the central/northern Plains. Pre-frontal warmth will be limited to
about 5-10 degrees above average for maxes but 5-15 degrees above
average for overnight mins. Some records may be possible across
Texas on Sunday and over Florida next Mon/Tue.

Ryan

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Fri Oct 18 2019

Valid 12Z Mon Oct 21 2019 - 12Z Fri Oct 25 2019

  • Upper Midwest/Great Lakes Storm
  • Potential Tropical Cyclone Sixteen to threaten the Northeast
  • Heavy rain and mountain snow from the Cascades to the North-Central Rockies


Guidance/Uncertainty Assessment and Weather Highlights/Threats:

An amplified and generally progressive flow pattern will support
several significant weather systems over the lower 48 states next
week.
The WPC medium range product suite was primarily derived
from a composite blend of reasonably well clustered guidance from
the GFS/ECMWF/UKMET/Canadian Monday and Tuesday in a pattern with
above normal forecast predictability
, albeit with uncertainty with
track/interaction of Potential Tropical Cyclone Sixteen as per
NHC. Switched to quite compatable GEFS/ECMWF ensemble mean
guidance later next week in a period of gradually increasing
forecast spread, but with a pattern evolution offering at least
average predictability given decent guidance continuity and system
organizations.

A closed upper low/trough will lift from the Plains through
eastern North America early to mid next week. Deep surface
cyclogenesis into the Upper Midwest/Great Lakes will act to ramp
up winds and unsettled weather/wrap-back snow while also forcing a
lead frontal system and Gulf of Mexico moisture return to combine
with upper support to fuel a widespread swath of heavy
rain/convection across the east-central states.
Activity over the
Northeast may be also significantly enhanced by
interaction/merging with a Mid-Atlantic to New England
extratropical coastal low and deepened moisture associated with
current Potential Tropical Cyclone Sixteen.

The pattern meanwhile reloads upstream as upper impulses/jet
energies/height falls work progressively inland over the
Northwestern U.S. early-mid next week that carve out another
amplified central U.S. upper trough mid-later next week.
A series
of systems/frontal passages offer a risk of heavy rain and
mountain snow from the Cascades to North-Central Rockies. Below
normal temperatures will sweep down through the interior
West/Rockies then Central U.S. Temperatures will become 10-15
degrees below normal over the north-central states as the post-frontal
high surges southward. Lead Gulf of Mexico moisture return into
the central Gulf Coast and lower MS/TN Valleys may fuel enhanced
rain/convection, with modest precipitation inland over the
east-central states
including some threat of wrapping snows for a
cooling Upper Midwest.

Schichtel

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1232 AM EDT Sat Oct 19 2019

Valid 12Z Tue Oct 22 2019 - 12Z Sat Oct 26 2019

  • Upper Midwest/Great Lakes storm early next week
  • Wet Southern to Eastern U.S. to include effect from remnants of T.S. Nestor
  • Northern then Central Rockies Heavy Snow...


Guidance/Uncertainty Assessment and Weather Highlights/Threats:

It remains the case that an amplified and generally progressive
flow pattern will support several significant weather systems over
the lower 48 states next week.
A closed upper low/trough will lift
from the MS Valley through eastern North America early to mid next
week. Deep surface cyclogenesis into the Upper Midwest/Great Lakes
will act to ramp up winds and rain with wrap-back wet snow while
forcing a lead frontal system and a return of Gulf moisture to
combine with upper support to fuel a widespread swath of heavy
rain/convection over the Eastern Seaboard
. Pre-frontal activity
and runoff issues over the Northeast may be significantly enhanced
by interaction with an extratropical coastal low associated with
current Tropical Storm Nestor. Recent model solutions indicate a
trend toward curving a weakening cyclone back into New England.

The pattern meanwhile reloads upstream as upper impulses/jet
energies/height falls work progressively inland over the
Northwestern U.S. early-mid next week that carve out another
amplified central U.S. upper trough mid-later next week
. A series
of systems/frontal passages offer a risk of Northern then Central
Rockies heavy snow. Below normal temperatures will sweep down
through the interior West/Rockies then Central U.S. Temperatures
will become 10-15 degrees below normal over the north-central
states as the post-frontal high surges southward. Lead Gulf of
Mexico moisture returning into the central Gulf Coast and lower
MS/TN Valleys then into the Appalachians/Eastern Seaboard should
fuel widespread enhanced rain/convection with potential for runoff
issues.

The WPC medium range product suite was primarily derived from a
composite of reasonably well clustered guidance from the 18 UTC
GFS/GEFS, the 12 UTC ECMWF/ECMWF ensemble mean and the National
Blend of Models in a pattern with above normal forecast
predictability
. This guidance blend acts to mitigate lingering
timing/strength variance to maintain good WPC system/pattern
continuity.

Schichtel

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Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Sun Oct 20 2019

Valid 12Z Wed Oct 23 2019 - 12Z Sun Oct 27 2019

  • An energetic pattern supports several significant lower 48 weather systems this week

Guidance/Uncertainty Assessment and Weather Highlights/Threats:

A lead upper trough will lift through the Northeast midweek as a
main deepened surface low works into Canada. Lingering
rains/runoff issues over the Northeast may be enhanced by
interaction and merging of a developing frontal wave from the
Mid-Atlantic with the extratropical remnants of Tropical Storm
Nestor. This scenario has high predictability.

Guidance also agrees that the flow pattern will meanwhile
reamplify well upstream as upper impulses/jet energies dig
progressively inland over the rapidly cooling West to support some
heavier snows into the n-central Rockies Wed/Thu.

Height falls should then act to carve out an amplified central
U.S. upper trough later week
. Pattern evolution uncertainty grows
quickly however, lower forecast confidence. Latest guidance trends
are mixed, but there is an overall signal showing southern stream
separation to some degree later week into next weekend as the main
trough shifts over the central states with a possibility of closed
low formation that would drastically up the ante with respect to
subsequent rainfall potential and runoff threat from the South
northeastward into the Eastern Seaboard with deep return of Gulf
of Mexico and Atlantic moisture
. WPC progs have trended to show
such potential. This is with consideration of the amplitude of
upstream upper ridging and as the next main kicker upper trough
does not bring unsettled weather/locally enhanced precipitation
through the Northwest until next weekend, so wavelength spacing
with the downstream system seems sufficient to allow for at least
some southern stream separation.

Schichtel

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