Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Nov 18 2024 21:57:06 AWUS01 KWNH 182157 FFGMPD MSZ000-LAZ000-TXZ000-190400- Mesoscale Precipitation Discussion 1157 NWS Weather Prediction Center College Park MD 455 PM EST Mon Nov 18 2024 Areas affected...Far Southeast TX...Southwest to Central LA Concerning...Heavy rainfall...Flash flooding possible Valid 182200Z - 190400Z SUMMARY...An increase in coverage of showers and thunderstorms can be expected going into the evening hours. Heavy rainfall rates and potentially some areas of cell-training may foster some localized potential for flash flooding. DISCUSSION...As a deep upper-level trough pivots northeastward through the central Plains and toward the Midwest, a cold front will be gradually approaching the northwest Gulf Coast region. This front will be interacting with a very moist and increasingly unstable airmass out ahead of it this evening, and the result is expected to be an increase in the coverage of heavy showers and thunderstorms. PWs are quite high right now across southeast TX with values near or slightly above 2 inches, and these magnitudes are as much as 2 to 3 standard deviations above normal for this time of the year. Meanwhile, MLCAPE values have risen to as much 1000 to 1500 J/kg and thus a moderate level of buoyancy has already pooled ahead of the front with the aid of daytime heating. A fairly strong southerly low-level jet of 30 to 40+ kts will be maintaining somewhat enhanced moisture transport off the Gulf of Mexico ahead of this front this evening. This coupled with the level of instability and favorable bulk shear should yield relatively organized bands or clusters of convection, including potentially some supercell activity, that will be capable of producing rainfall rates of 1 to 2 inches/hour. Initially the activity will be more focused over areas of far southeast TX, but should in time concentrate increasingly over southwest to central LA. Some of the more organized activity may involve some cell-training as the convection becomes aligned with the deeper layer mean flow, and this may result in the potential for locally excessive totals. The 12Z/18Z HREF guidance supports some 2 to 4 inch rainfall amounts with isolated heavier totals. A localized and mostly urban flash flood threat will exist as these bands of convection come through this evening. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6jucQIqEYwpxCvflmYFiKiE8VFtMqgbz0oaNbKbL_kmV0P55GzA3aCGc1dkx8VLC1nES= J4HizpGEPbfo3Q_5v0bbbow$ for graphic product... ATTN...WFO...JAN...LCH...LIX...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 32289212 32109155 31229155 30039244 29619285=20 29709339 29649395 29909426 30469430 31049394=20 32059292=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) .