WPC Met Watch

WPC Met Watch


Mesoscale Precipitation Discussion: #0249 (Issued at 322 PM EDT Thu May 09 2024
) MPD Selection


Graphic for MPD #0249

Mesoscale Precipitation Discussion 0249
NWS Weather Prediction Center College Park MD
322 PM EDT Thu May 09 2024

Areas affected...Southeast AL...Southern GA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 091920Z - 100000Z

SUMMARY...Upstream redevelopment along flanking edge will be fed
by highly unstable, deep rich moisture environmental air for
additional development.  Slight backing of steering could align
favorably for training and spots of 3-4" and possible incidents of
flash flooding through the evening.

DISCUSSION...Regional RADAR mosaic depicts a mature to decaying
squall line continuing to surge southeastward across the Coastal
Plain of Southern SC and E GA.  The direction of the cold pool
remains directed southeasterly as driver shortwave/MCV and
associated outflow channel continue to slide northeast to
east-northeast through the Carolinas.  However, this leaves the
trailing outflow boundary and shallow cold pool draped and angling
back from the base of the bow near DQH off toward the NW south of
ABY and EUF before becoming more diffuse over central AL between
EET/LX and MGM.  19z surface winds and VWP also denote
southwesterly flow fairly perpendicular to the outflow boundary
especially across SE AL southwest of EUF and east of TOI; with a
bit of confluence of the flow as it is more westerly further north
and southwesterly further south out of FL.

This flow is fluxing highly unstable air with MLCAPE of 2500-3000
J/kg as well as Total PWAT values of AoA 2.0". Given the cold
pool/isentropic ascent column for upstream
back-building/thunderstorm regeneration with tops below -65C,
likely supporting potential for 2-2.5"/hr rainfall rates. 
Additional to the favorable ascent column; in the wake of the
exiting shortwave, GOES-E WV depicts upstream ridging and deeper
flattening of the flow to support more west to east flow.  This
will bring cell motions back across areas that have recently seen
solid 1.5-3" with the initial round.  As such such an additional
2-4" may result in spots of up to 4-5" in total.  While the area
has been dry and typically has higher capacity, this one-two punch
in quick succession may result in a few incidents of flash
flooding into the evening hours. 

Confidence is reduced slightly given the lack of support for these
higher totals in the Hi-Res CAM solutions.  However, most have
suggested stronger southward push to the cold pool and less
upstream redevelopment (likely to the angle of isentropic ascent
to the boundary) compared to recent observational trends. 




LAT...LON   32738561 32708488 32488367 32268306 31968258
            31428245 31078290 31078364 31298449 31508502
            32088582 32468597

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Last Updated: 322 PM EDT Thu May 09 2024

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