Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Dec 26 2024 23:58:58 AWUS01 KWNH 262358 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-270500- Mesoscale Precipitation Discussion 1194 NWS Weather Prediction Center College Park MD 658 PM EST Thu Dec 26 2024 Areas affected...southeastern TX into western LA Concerning...Heavy rainfall...Flash flooding likely Valid 262356Z - 270500Z SUMMARY...Training and repeating of thunderstorms will continue a flash flood threat from southeastern TX into western LA through 05Z. Rainfall rates of 1-2 in/hr and localized totals of 2-4 inches can be expected. DISCUSSION...Regional radar imagery at 2330Z across the South showed a line of thunderstorms extending from northwestern LA into the Piney Woods of southeastern TX with a second line extending from Jasper/Newton counties to roughly Matagorda Bay. These storms were occurring just ahead of a pre-frontal trough/wind shift located east of a cold front moving through east-central TX. SPC mesoanalysis data from 23Z showed PWATs of 1.4 to 1.7 inches coincident with the thunderstorm axis and MLCAPE of 500-2000 J/kg from the central TX/LA border to the mid TX coast. Favorable shear profiles ahead of a potent mid-level vorticity max (over north TX) have supported supercells with enhanced rainfall rates while mean steering flow from the southwest has resulted in areas of training and/or repeating rounds of heavy rain from the northern TX/LA border into the southeastern TX Coastal Plain. Over the next 3-5 hours, the best upper level support (PVA, upper diffluence/divergence) will shift eastward from the Arklatex into northern LA/southern AR. However, RAP forecasts of instability show only a small pocket of 500-1000 MUCAPE just ahead of the mid-level low center which should be steadily tracking east through the first half of tonight. Due to lower instability profiles, a lower end flash flood threat will exist for these northern locations where strong forcing will should be balanced by a fairly progressive translation of heavy rain toward the east and limited instability. Farther south, a lack of height falls for the Gulf Coast region should result in a slower eastward progression of heavy rain. It is here where greater instability is forecast to reside within the warm sector (500-1500 J/kg MLCAPE). 850 mb winds of 40-60 kt from the southwest and similarly oriented mean steering flow will allow for areas of training and repeating thunderstorms capable of 1-2 in/hr (perhaps locally above 2 in/hr) due to a slower eastward progression to the axis of thunderstorms. 2-4 inches of rain over a roughly 2 hour window is expected to result in a couple of areas of flash flooding through 05Z from southeastern TX into western LA. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-CVMsN44zV6cl5EGyQ9kxK4q073aGWwSlZREmXdpQRwVl8YWclCSHggBiLiwR3Lwqe2B= _T9ceaMmzLObBgV_elWJF50$ for graphic product... ATTN...WFO...HGX...JAN...LCH...LZK...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 33949177 33509109 32649100 31619139 30769200=20 29699292 29499407 29039513 29219549 30059521=20 31439447 32449392 33769307=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .