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Severe Weather for Sunday, April 14

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5 hours ago, KingOfTheMountains said:

Getting really worried for the Northern Louisiana region on Saturday. I've got friends in that area and the HRRR is trending more unstable by the hour. Hopefully it's overdone.

 

 

That area is going to get hit hard.

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Good Saturday morning! The good news, the "Enhanced" area has shifted north.... the bad news is that north Georgia is still in it.

Here's the latest...

Quote

 ...Mid and upper Ohio Valley and central Appalachians, southward
   into the Southeast...
   A semi-continuous, roughly north-south band of thunderstorms is
   expected to be ongoing at the start of the period, extending from
   southeastern Indiana/southwestern Ohio southward to the
   Alabama/western Florida Panhandle coasts; while this will likely be
   a period of relative minimum in severe risk, local risk for damaging
   winds/hail, and possibly a tornado or two, will likely be ongoing.

   As the airmass ahead of this initial band destabilizes into the
   afternoon, storms are expected to reintensify.  Damaging winds and
   some tornado risk may spread across the middle and into the upper
   Ohio Valley through the afternoon with this band of storms. 
   Meanwhile near and east of the southern Appalachians,
   reintensification of convection in this band may become more
   cellular in organization.  Given favorably strong flow through the
   lower and middle troposphere contributing to strong shear, this more
   cellular storm mode would support risk for a few tornadoes, along
   with locally damaging winds and some hail.

   In the wake of this initial band of storms, modest destabilization
   is expected, likely leading to development of a second band of
   storms nearer the surface cold front.  As this band of storms
   crosses the middle Ohio Valley/Mid South region, severe risk is
   anticipated, with damaging winds and tornadoes both possible given
   the very strong shear residing atop the pre-frontal boundary layer. 
   Risk in any area will be somewhat storm-mode dependent, with a mix
   of cellular and banded structures possible within the north-south
   zone ahead of the front.

   During the evening, as the front progresses, the convection -- and
   accompanying severe risk -- will spread east of the mountains,
   bringing a potential second round of severe weather to some areas. 
   While risk should decrease across NY/PA overnight, some threat will
   likely linger through the end of the period from VA southward into
   the Carolinas.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     30%     - Enhanced
   Hail:     30%     - Enhanced

GA_swody2-13.png.8c8e4090cc46de41994043ad4c1a821c.png

 

NWS Atlanta. They will also have another briefing today around 2 pm or so that I will post here. 

Quote

Models have been consistently showing a pre-frontal trough/squall
line approaching the CWFA early Sunday morning. The higher res
models do differ on the timing of the system by a few hours, but all
show a mostly continuous line of thunderstorms moving through the
CWFA during the day on Sunday. The higher res models are also
hinting of the possibility of the initial pre-frontal trough/squall
line weakening across far NW GA during the late morning before
convection re-fires along the actual cold front and/or outflow
boundary in the afternoon, during peak heating/instability. With a
strong wind field aloft, good forcing in the mid levels and good
surface instability, the potential for severe weather remains high.
The primary mode for severe weather would be damaging wind gusts in
excess of 60mph. Large hail and an isolated tornado are not out of
the question either.

The line of thunderstorms should move out of the CWFA during the
late afternoon/early evening hours. High pressure and drier
conditions will move in fairly quickly behind the system on Sunday
night.

 

Further west over LA/MS/TX, this same system that will bring our severe weather on Sunday, is going to make for a very rough day for folks in that area. 

fema04_swody1.png

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Saturday, 5:44 am
NWS Huntsville - 
http://wx.northgeorgiawx.com/afd_hun2.html/

Quote

A possibly significant outbreak of severe storms will be occurring
across the ArkLaMiss as we start the tonight period. The strong
trough, good jet dynamics, and influx of deep moisture will result in
an environment very conducive for supercellular development to our
west. Over the TN Valley though, the strengthening SW flow aloft will
result in an influx of moisture with PWATs near our climo Max for
this time of year. This translates into lapse rates that won't be
nearly as steep as those to our west, and thus instability is
forecast to be slightly lower (700-900 J/kg) compared to 2,000 J/kg
out west. Wind shear though will be very strong with 0-6km shear
values up to 60kts overnight and closer to 90 kts Sunday afternoon.
Veering of winds in the lower to mid levels will mean hodographs
supportive of supercellular like structures/mesocyclones.


As the system progresses eastward we'll see the low/mid level flow
begin to become more N/S orientated. This should result in the
individual clusters of storms starting to form into more linear
segments. The global scale models have been holding steady in the
timing and don't have storms impacting the area until 06z tonight.
However, a few of the CAMs suggest a possibility of storms moving in
slightly before that (04-05z). Still think the slightly earlier
arrival could happen as models tend to be on the slow side when
dealing with these kind of lines of storms.


While the latest SPC outlooks continue to suggest the greatest threat
for severe storms will be to our SW based on the shear profiles and
overall strength of the upper level system believe that the entire TN
Valley could see severe weather tonight. Latest HREF updraft helicity
probs would point to supercells embedded within the line as the line
moves across northern MS. But as the line moves into a lower
instability environment it loses some of it's strength and the
threat for severe storms may be lower for locations east of I-65
overnight. Something that is still worth mentioning is that the
NAM/GFS/ECMWF show an almost bi-modal depiction of storms overnight
with one cluster moving out of MS, clipping NW AL and shifting into
central TN. The other develops over southern MS and feeds off the
greater instability down south, which may further limit the strength

of storms across NE AL. Remains to be seen if this even occurs but
worth watching. We've still had situations where, a weakening QLCS
perks back up as it begins to encounter the terrain and the localized
enhanced low level wind shear environment generated by the terrain.
So, we are still going to highlight the potential for severe storms
for the entire area, with damaging winds, tornadoes, and localized

flooding the main threats. All of the guidance has storms exiting the
area to the east close to sunrise Sunday.

While this would initially be welcome news, the true cold front and
core of the upper level low are both progged to move across the area
during the afternoon hours. Behind the morning line of storms drier
air moves in aloft ahead of the upper level low and with strong
southerly winds continuing we'll see this drier air mix down to the
surface. Guidance shows dewpoints falling into the mid to upper 50s
in the afternoon. While the lapse rates steepen significantly through
the day as the core of the low moves overhead, the mixing down of
this drier air at the same time will reduce instability somewhat.
So, instead of 60 degree dewpoints and CAPE of 800-1000 J/kg we may
end up with 54-58 degree dewpoints and CAPE values of 400-500 J/kg.
As mentioned briefly above, deep layer shear ramps up significantly
with 0-6km shear upwards of 90kts! The drier air should help to
erode any lingering cloud cover and allow for temps to warm into the
mid to upper 70s. As the front moves in another round of storms is
expected to develop during the afternoon hours. Due to a more
unidirectional wind profile, the main threats will likely be damaging
winds and large hail for Sunday afternoon. The best chances for
severe weather during the afternoon hours in this case will be for
locations East of I-65.

 

5:48 am Saturday
NWS Birmingham - 
http://wx.northgeorgiawx.com/afd_bmx.html/

Quote

A potent southern stream shortwave trough currently moving into West
Texas will continue to push eastward today. By tonight it will be
mainly neutrally tilted as it approaches the Mississippi River
though the far southern end has a positive tilt. A sub-1000mb
surface low will track into the ArkLaTex this afternoon and into the
Mid-South by Sunday morning. A pre-frontal band of supercells will
develop over Louisiana this afternoon and move into Mississippi by
this evening. 

As the southern stream trough begins to phase with the
northern stream trough, the mid and upper-level jets will strengthen
along the Mississippi River this evening, to 120kts at 300mb and 95
kts at 500mb. The low-level jet will strengthen to 55-60 kts at 850
mb and 45-50kts at 925mb. The associated increasing dynamics will
maintain the line of storms as it moves into Alabama and would
favor upscale growth. But it appears 0-6 km bulk shear vectors of
60-70+ kts oriented approximately 45 degrees to the line will
result in a semi-broken line with embedded supercells. While this
may prevent a more widespread damaging wind threat, it will
enhance the tornado threat. Advection of higher theta-e air by the
strong low-level jet will support an axis of 500-1000 J/kg of
CAPE with pockets of locally higher values. This is fairly decent
considering the time of the day, and the strong shear will also
offset the modest instability. Strong to extreme low-level shear
will be present with 0-1km SRH around 300 m/s2 and 0-3 km SRH
around 400 m2/s2 with locally higher values, resulting in large
curved hodographs. Therefore, a strong tornado or two will be
possible mainly in West Alabama. Want to emphasize that these
potential tornadoes will NOT just be quick QLCS spin-ups but more
supercellular in nature.

Of course there are always uncertainties with any severe threat,
especially at night. The instability axis will be somewhat narrow
and will need to keep up with the storms, and small differences in
surface temps/dew points can make a big difference in CAPE values. H
ow convection evolves upstream adds uncertainty. It's also possible
there may be a post-sunrise relative minimum in convective activity
where the threat may be slightly less, but it's hard to say at which
location that would be. All in all, the data supports maintaining
the enhanced risk across the whole area, especially given the
overnight timing. Made a few tweaks to the threat timing, indicating
a slightly faster overall trend (1AM - 1PM). 
It is imperative that everyone in Central Alabama 
has a way to receive warnings that can
wake them up tonight.
The strong convection and LLJ should be east of the area by
afternoon. A mid-level dry slot will move into the area, allowing
temperatures to warm up, before the cold front and some wrap-around
moisture and associated precipitation arrives. Some guidance
indicates a band of convection developing along the front, but this
guidance (NAM/NMM) typically recovers the air mass too quickly,
compared to the more reliable ARW models. So severe storms appear
unlikely for Sunday afternoon, but do expect some showers and
isolated thunderstorms to develop.

 

Please, if you live in Alabama or southern TN, be alert tonight. 

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Many of the weather radio transmitters are down for the Huntsville area this morning, and no idea when they will be back up. This is another reason to never rely on one method of receiving weather information. 

Quote

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1035 PM CDT FRI APR 12 2019

...A NUMBER OF WEATHER RADIO SITES ACROSS THE TENNESSEE VALLEY 
ARE OFF LINE... 

A NUMBER OF NOAA WEATHER RADIO STATIONS ACROSS THE TENNESSEE
VALLEY ARE CURRENTLY OFF LINE. TRANSMITTER SITES THAT ARE NOT 
BROADCASTING INCLUDE:

KIH-57, NEAR FLORENCE ON A FREQUENCY OF 162.475 MHZ.
WNG-642, IN ARAB, ON A FREQUENCY OF 162.525 MHZ.
WWF-66, IN CULLMAN, ON A FREQUENCY OF 162.450 MHZ.
WWF-44, NEAR FORT PAYNE, ON A FREQUENCY OF 162.500 MHZ.
WNG-554, IN WINCHESTER, ON A FREQUENCY OF 162.525 MHZ. 

WEATHER STATION KIH-20 IN HUNTSVILLE, ON A FREQUENCY OF 162.400
MHZ HOWEVER REMAINS ON THE AIR, AND HAS NOT BEEN AFFECTED BY THIS
OUTAGE. 

THE CAUSE OF THE OUTAGE IS UNKNOWN. WE HAVE CONTACTED TECHNICIANS
TO FIX THE PROBLEM. IT IS UNKNOWN WHEN SERVICE WILL BE RESTORED. 

DURING THE OUTAGE, PERSONS ACROSS THE LISTENING AREA WILL NEED TO
TUNE TO COMMERCIAL RADIO OR TELEVISION OUTLETS FOR THE LATEST
WEATHER INFORMATION.

THE LATEST WEATHER INFORMATION IS ALSO AVAILABLE AT OUR WEBSITE
AT, HTTP://WEATHER.GOV/HUNTSVILLE 

WE APOLOGIZE FOR ANY INCONVENIENCE THIS OUTAGE MAY CAUSE.

 

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Here is the situation for today:

swo_sm_201904130743.png.202dfbfc310aa1c230ef08958886c897.png

Quote

   PUBLIC SEVERE WEATHER OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0242 AM CDT SAT APR 13 2019

   ...Severe thunderstorms expected over parts of the East Texas to
   lower Mississippi Valley region later today and tonight...

   * LOCATIONS...
     Central and northern Louisiana
     Mississippi
     East Texas
     Southern Arkansas
     Western Alabama

   * HAZARDS...
     Several tornadoes, a few intense
     Widespread damaging winds
     Scattered large hail, some baseball size

   * SUMMARY...
     Numerous severe thunderstorms capable of producing tornadoes,
     wind damage and large hail, are expected across parts of east
     Texas, Louisiana, southern Arkansas, Mississippi, western
     Alabama and surrounding areas today and tonight. The greatest
     risk is from east Texas to central Mississippi.

   Preparedness actions...

   Review your severe weather safety procedures for the possibility
   of dangerous weather today. Stay tuned to NOAA Weather Radio, 
   weather.gov, or other media for watches and warnings. A tornado
   watch means that conditions are favorable for tornadoes to form
   during the next several hours. If a tornado warning is issued for
   your area, move to a place of safety, ideally in a basement or
   interior room on the lowest floor of a sturdy building.

 

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20 hours ago, NorthGeorgiaWX said:

Thought I'd create a new topic for this event so that we can keep all of the talk and updates here. I'll still add some comments etc in the morning update each day, but the main discussion will be here.  Much of this first post is a re-cap from the morning post, but I'll still go ahead and re-share here. 

As of now... the Storm Prediction Center has placed the north Georgia area under an "Enhanced" risk for severe weather on Sunday. 

GA_swody3-12.png.5f615d5a18772d0c86aef6ba26860d36.png

 

UPDATED VERSION as of 4/13/19 5:40 am

GA_swody2-13.png.a67aa2a4aef5511ec4fb83c164055653.png

 

We probably won't see a 3 day update again, as the next update is 4:30 am tomorrow, so we'll start looking for the Day 2 updates late today. 

Again, it's ALWAYS good to check the upstream forecast offices for their updates, they see the storms before we do, so knowing what they are thinking goes a long way toward what we may see here.

Huntsville AFD - http://wx.northgeorgiawx.com/afd_hun2.html/

 

This in the hazardous Weather Outlook from the Atlanta NWS office

ffc_sunday_12.thumb.jpg.235eafc2828da0f22d2bad26adf59da2.jpg

 

So keep checking back here and make sure you "follow" this topic. 

As always Steve thank you for keeping us informed the way you do, you're the best!!

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Hi, Steve.  Any idea yet about timing for us tomorrow?  Thanks for all you do!

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Any chance of the thing Glenn Burns posted about actually happening? The southern storms making ours weaker?

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What about Chattanooga headed there this afternoon staying until 4 tomorrow then travelling back to dacula

 

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3 hours ago, LEmbs said:

Hi, Steve.  Any idea yet about timing for us tomorrow?  Thanks for all you do!

 

30 minutes ago, Asperman1 said:

Any chance of the thing Glenn Burns posted about actually happening? The southern storms making ours weaker?

 

18 minutes ago, JenRay said:

What about Chattanooga headed there this afternoon staying until 4 tomorrow then travelling back to dacula

 

See my last post. 

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After reviewing the latest Atl update, it seems as if they expect the threat level to go higher...? Is that correct? Thanks.

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Snap346062608-13.thumb.jpg.724ec29c98212e95d00266f057bb4b6a.jpg

 

Quote

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
256 PM EDT SAT APR 13 2019

DADE-WALKER-CATOOSA-WHITFIELD-MURRAY-FANNIN-GILMER-UNION-TOWNS-
CHATTOOGA-GORDON-PICKENS-DAWSON-LUMPKIN-WHITE-FLOYD-BARTOW-
CHEROKEE-FORSYTH-HALL-BANKS-JACKSON-MADISON-POLK-PAULDING-COBB-
NORTH FULTON-GWINNETT-BARROW-CLARKE-OCONEE-OGLETHORPE-WILKES-
HARALSON-CARROLL-DOUGLAS-SOUTH FULTON-DEKALB-ROCKDALE-WALTON-
NEWTON-MORGAN-GREENE-TALIAFERRO-HEARD-COWETA-FAYETTE-CLAYTON-
SPALDING-HENRY-BUTTS-JASPER-PUTNAM-HANCOCK-WARREN-TROUP-
MERIWETHER-PIKE-UPSON-LAMAR-MONROE-JONES-BALDWIN-WASHINGTON-
GLASCOCK-JEFFERSON-HARRIS-TALBOT-TAYLOR-CRAWFORD-BIBB-TWIGGS-
WILKINSON-JOHNSON-EMANUEL-MUSCOGEE-CHATTAHOOCHEE-MARION-SCHLEY-
MACON-PEACH-HOUSTON-BLECKLEY-LAURENS-TREUTLEN-STEWART-WEBSTER-
SUMTER-DOOLY-CRISP-PULASKI-WILCOX-DODGE-TELFAIR-WHEELER-
MONTGOMERY-TOOMBS-

INCLUDING THE CITIES OF CALHOUN, DAHLONEGA, CLEVELAND, ROME, 
CARTERSVILLE, GAINESVILLE, MARIETTA, ATLANTA, LAWRENCEVILLE, 
ATHENS, CARROLLTON, DOUGLASVILLE, EAST POINT, DECATUR, CONYERS, 
COVINGTON, NEWNAN, PEACHTREE CITY, GRIFFIN, MILLEDGEVILLE, MACON,
SWAINSBORO, COLUMBUS, WARNER ROBINS, DUBLIN, LUMPKIN, AMERICUS, 
CORDELE, AND VIDALIA

256 PM EDT SAT APR 13 2019

...WIND ADVISORY IN EFFECT FROM 4 AM TO 10 PM EDT SUNDAY...

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A WIND
ADVISORY, WHICH IS IN EFFECT FROM 4 AM TO 10 PM EDT SUNDAY.

* WINDS...SOUTH TO SOUTHWEST 15 TO 20 MPH WITH GUSTS UP TO 35 MPH.

* TIMING...4 AM TO 10 PM SUNDAY.

* IMPACTS...GUSTY WINDS WILL BLOW AROUND UNSECURED OBJECTS. IF 
  GROUNDS ARE MORE SATURATED FROM RAIN, THEN TREES WILL BE MORE
  PRONE TO BEING KNOCKED DOWN OR UPROOTED. A FEW POWER OUTAGES
  MAY RESULT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT SUSTAINED WIND SPEEDS OF AT LEAST
20 MPH...OR GUSTS TO 35 MPH OR STRONGER ARE EXPECTED. WINDS THIS
STRONG CAN MAKE DRIVING DIFFICULT...ESPECIALLY FOR HIGH PROFILE
VEHICLES. USE EXTRA CAUTION.

 

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Even with convection possibly robbing the morning band, I'm assuming that would have little to no impact on the afternoon redevelopment? I feel just given the peak heating that 2nd round could be stronger for those that get it. 

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Posted (edited)
33 minutes ago, KingOfTheMountains said:

Even with convection possibly robbing the morning band, I'm assuming that would have little to no impact on the afternoon redevelopment? I feel just given the peak heating that 2nd round could be stronger for those that get it. 

That's exactly what I see. The ingredients are ripe during that exact timing...peak day time heating. I don't think the morning band will be too strong for us here in Blue Ridge, but that second one just may be. Luckily, much less of a tornado threat with that line.

Edited by SuperCell
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Update - 3:52 pm Saturday

Quote

Main focus of course on severe threat Sunday from potent frontal
system and attendant impressive upper dynamics. SPC continues to
have Enhanced Risk across north GA and Slight elsewhere, though
any location in CWA could have some scattered severe storms. The
first most likely prefrontal round would be pushing into the
northwest as early as 12z  (8am) then proceed eastward. Impressive shear
in both deep and low layers ramping up after 15z (11 am) with upwards of
500 m2/s2 of 0-1 km SRH. This combined with rather ample CAPE in
1000-1500 J/kg range will bring a threat to not only damaging
winds in any bowing segments, but also brief spin-up tornadoes.
Sig Tor Param is rather high in multiple models also in the 2-4

range. There is potential for a second round of convection firing
off later in the afternoon closer to the front and still east of
the upper trough axis. Will need to watch this as if mid level
lapse rates do steepen, there could be perhaps some hail potential

with the storms. Regardless of the storms, there will be enhanced
gradient winds out of the south to SW and with sustained of near
20 mph gusting up to 35 mph, have warranted a Wind Advisory area-

wide through Sunday. Cooler temps building in for Sunday night as
things clear out from the west and most areas will fall into the
mid 40s.

 

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1 hour ago, SuperCell said:

That's exactly what I see. The ingredients are ripe during that exact timing...peak day time heating. I don't think the morning band will be too strong for us here in Blue Ridge, but that second one just may be. Luckily, much less of a tornado threat with that line.

I have to ask, if it is cloudy all day, will day time heating still happen? Sorry if it is a dumb question, just curious

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1 hour ago, Asperman1 said:

I have to ask, if it is cloudy all day, will day time heating still happen? Sorry if it is a dumb question, just curious

Not a dumb question at all, and in fact is usually very important. But in this case probably no help. Lows tonight will only get into the 60s which is already warm enough, and the warm front driving north will almost certainly put us all in the 70's with dew points in the 60's by afternoon which is plenty soupy. 

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3 minutes ago, KingOfTheMountains said:

Not a dumb question at all, and in fact is usually very important. But in this case probably no help. Lows tonight will only get into the 60s which is already warm enough, and the warm front driving north will almost certainly put us all in the 70's with dew points in the 60's by afternoon which is plenty soupy. 

Dang... any good news to share?

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Things certainly weren't as bad as they could have been in the Louisiana area today. A handful of tornado warned storms but certainly no regional outbreak. All it takes is one though if populated areas get hit, so not out of the woods in that region yet. Looks like there were actually too many storms competing for energy, and those interactions made the storm mode more of a QLCS instead of discreet well-ventilated super cells. 

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