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NorthGeorgiaWX

Sunday, December 22

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Good morning! Let's get right to it.

Here's the setup. You can see the big closed upper level low that's drifting SE right now and the rain shield to the right of it. That shield will be advancing our way and we'll stay in the rain for at least 36-48 hours.

Snap346063245.thumb.png.bd2d40218a4f7076422ebbf264116a2f.png

 

This is the WPC excessive rainfall discussion:

Quote

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
315 AM EST Sun Dec 22 2019

Day 1
Valid 12Z Sun Dec 22 2019 - 12Z Mon Dec 23 2019

  • THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN COASTAL GEORGIA AND SOUTH CAROLINA

Southeastern States:
A widespread rain event is underway across much of the Southeast
early this morning as a strong closed low draws a plume of deep
moisture north.
Precipitable water and integrated moisture
transport values in the deep moisture plume should be above the
95th percentile for December. This will deliver a corridor of
substantial rainfall in the area of persistent low-mid level
thetae advection and a coupled upper level jet structure over
Alabama, Georgia and parts of South Carolina. In that region,
areal average rainfall amounts of 1 to 3 inches appear likely,
with locally higher amounts possible.
This will lead to a broad
possibility of flooding issues over the Southeast due to a gradual
accumulation of rainfall over a larger portion of the outlook
period.

The primary limiting factor for flash flood potential is a lack of
instability, and models generally keep values above 100-200 j/kg
offshore or to the south of the Interstate-4 corridor in the
central Florida Peninsula. This should limit the potential hourly
rain rates, and hi-res models tend to show maximum rates around
0.5 inches in the region of highest expected 24-hour rainfall
totals. The potential exceptions would be: (1) in south Florida
where instability will be higher and some hi-res models produce
rain rates to around 2 in/hr; (2) along the Georgia and South
Carolina coastline where secondary coastal low development may
sufficiently focus low-level convergence and an instability
gradient to produce heavier rain rates along the immediate coast.

To balance these factors, a broad Marginal Risk was maintained
over much of the Southeast and was expanded south through the
remainder of South Florida and the Florida Keys. And the Slight
Risk and Moderate Risk areas were concentrated close to the
Georgia and South Carolina coastlines. The existing Slight Risk
was therefore trimmed some in inland areas; however an extension
was maintained into central Georgia to account for a corridor from
Macon to Augusta where rainfall has been above average over the
past month and streamflow is more elevated. Several inches of
rainfall, even in the absence of significant rain rates, falling
on these parts of C GA could lead to more flooding issues.

The greatest concern exists along the Georgia and South Carolina
coasts where a Moderate Risk has been maintained. The threat
should be highest after about 21Z and through tonight as a coastal
low begins to develop on the Atlantic side, and low-level
convergence begins to increase. If heavier rain rates can
materialize, they could combine with strong onshore flow during an
overnight high tide cycle to produce a combination of coastal
inundation. The Moderate Risk was extended north into the
Charleston metro area to account for this possibility.

 

This from the Atlanta NWS office:

Quote

Area Forecast Discussion
National Weather Service Peachtree City GA
255 AM EST Sun Dec 22 2019

 

  • Locally Windy Conditions and Saturated Soils Will Lead To Downed Trees

Regional synoptic analysis indicates closed upper low now moving
into the lower Mississippi Valley which is increasing the diffluence
aloft over the local area. Meanwhile, the surface reflection of this
feature is over the northern Gulf of Mexico and while high over
Carolinas acts in tandem with this to wedge in the local area.
Increasing isentropic upglide is the end result with expanding light
rain shield moving in. QPF very light to this point and zero
instability nearly region wide is preventing any lightning at this
time.

For the remainder of today, surface low will trek slightly north and
east into the Florida panhandle and strengthen the gradient
significantly with aforementioned Carolinas high. Of more concern is
the low level jet all the way down to 925mb that is in excess of 60
kts at times and moves into the Central GA zones and up to I20 by
the afternoon hours. Inversion and strengthening wedge should keep
most of this aloft but still somewhat concerning, especially for
eastern zones as we get some measure of instability late today.

Newest gusts values fall short of high wind warning and will
transition to Wind Advisory for now. Strongest winds will actually
be this evening, so still an opportunity for day shift to upgrade if
need be. Regardless of the product out, downed trees are to be
expected with the saturated soils and will be highlighted in
advisory and HWO.

Otherwise, a soaker definitely in store for the next 48 hours with
values perhaps slightly less than previous model runs but still a
solid 3 plus inches along I16 with locally higher amounts should we
get any convective elements going later today. Dry slot to move in
form the south on Monday up to the southern Atlanta metro, but still
socked in for the North Ga portion with likely to categorical pops
right through Mon afternoon.

 

 

The official NDFD rainfall forecast looks like this.

ndfd-conus-georgia-total_precip_inch-7232000.thumb.png.8d4d61cc3861fc5f17158cb3cd370c00.png

 

The official wind gust forecast looks like this. Below this image are the various models just to give you an idea what the models are seeing. 

ndfd-conus-georgia-gust_swath_mph-7232000.thumb.png.f2404f7cbca27843b5dbfc2d70ea7b02.png

 

ncep-wrf-arw-conus-georgia-gust_swath_mph-7113200.thumb.png.23717023176a54e13d93a652e353dbef.pngnam-218-all-georgia-gust_swath_mph-7113200.thumb.png.1d0cfe4a899909d91c1855ef46a29d65.pngnam-nest-conus-georgia-gust_swath_mph-7113200.thumb.png.e1bbbd27ff67658228b7f9fc96b6df87.pngnbm-conus-georgia-gust_swath_mph-7113200.thumb.png.f6a8bcf0be79da16ab0213db694a0a44.pnggfs-deterministic-georgia-gust_swath_mph-7113200.thumb.png.86171dc4fcd90a9397b68dc1c29f3b98.pngecmwf-deterministic-georgia-gust_swath_mph-7232000.thumb.png.48cf45ed62656422a64f02f407ed1a47.png

 

The same basic watches are in place that were issue yesterday.

270064705_MapImage(1).jpg.3011506585482177c382f64e2805bc3c.jpg1572889446_MapLegend(1).jpg.75a69331747701f56c3bfc584174f966.jpg

 

So that's the story. I'll continue to have updates all day long!

I saw put on a rainsuit and go out and play in the rain! Enjoy the weather!
Have a great Sunday!

Snap346063246.png.4ab9f834e96430afdb416108ddb736ed.png

 

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LSRFFC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
325 PM EST SUN DEC 22 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0301 PM     NON-TSTM WND GST 3 NNE MARBLEHILL        34.47N 84.33W
12/22/2019  M54 MPH          PICKENS            GA   MESONET

            MESONET STATION FW3168 JASPER.
------------------------------------------------------------------------

NWUS52 KFFC 222035
LSRFFC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
330 PM EST SUN DEC 22 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0202 PM     NON-TSTM WND GST 1 WSW HARTSFIELD-JACKSO 33.63N 84.45W
12/22/2019  M35 MPH          CLAYTON            GA   ASOS

            ASOS STATION KATL ATLANTA.

-----------------------------------------------------------------------

LSRFFC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
335 PM EST SUN DEC 22 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0112 PM     NON-TSTM WND GST 1 W COLUMBUS METROPOLIT 32.52N 84.95W
12/22/2019  M38 MPH          MUSCOGEE           GA   ASOS

            ASOS STATION KCSG COLUMBUS.

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9 hours ago, Christine said:

Any snow opportunities on the horizon?? I know things are always changing but I love the excitement of the possibility! 😊

Not at the moment... although it does look like temperatures will be much colder in January. 

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