Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Dec 24 2023 10:04:23 AWUS01 KWNH 241004 FFGMPD TXZ000-241600- Mesoscale Precipitation Discussion 1219 NWS Weather Prediction Center College Park MD 503 AM EST Sun Dec 24 2023 Areas affected...southeastern TX Concerning...Heavy rainfall...Flash flooding possible Valid 241000Z - 241600Z SUMMARY...A localized flash flood threat will exist across the upper TX coast this morning with potential for 1-2 in/hr rates and localized 2-4" totals through 16Z. DISCUSSION...GOES East water vapor imagery showed two features of note at 0930Z. First was a mid to upper-level trough crossing into the southern High Plains with widespread ascent downstream. Second was an upper level vorticity max centered ~100 miles south of the western LA coast. RAP analysis data showed and LPW imagery confirmed, the presence of a strengthening gradient in surface to 850 mb moisture, oriented NW to SE from the upper TX coast into the central Gulf of Mexico. This gradient is related to a forming low level warm front, which when taking into account the offshore vorticity max, is associated with an area of moderate to heavy rain in the vicinity of Galveston Bay and offshore into the northern Gulf. Roughly 1-2 inches of rain have been reported so far in and around Galveston Bay. SPC mesoanalysis data from 09Z showed 500 to 1000+ J/kg MUCAPE located on the warm side of the developing warm front along with PWATs of 1.5 to 1.7 inches along the upper TX coast. The warm front is forecast to lift northward into the northern Gulf of Mexico and the upper TX coast through 15Z. As this occurs, instability of 500 to 1000+ J/kg is forecast by the HRRR/RAP to reach Galveston Bay. Despite the departing vorticity max south of western LA, the 925-850 mb boundary is expected to continue acting as a source of lift while larger scale ascent is favored by upper level divergence within the left exit region of a strong subtropical jet max crossing northern Mexico and widely diffluent flow aloft over the upper TX coast downstream of the approaching trough axis to the west. Development of additional showers/thunderstorms will be possible after 12Z with SSWLY deeper layer steering flow potentially allowing for localized areas of training in the vicinity of the upper TX coast with low level flow advecting from the source region of better moisture/instability to the south. Peak rainfall rates of 1-2 in/hr may support isolated 2-4 inch totals through 15 or 16Z, along with localized flash flooding. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7PWU6WPWn0t-TIVN5tnsVJeDAFZlqc1r5fEykkWbzwa2s75uEvWIOOQJyAoVYZzs-rBK= Py5oUmU6x5gmnQbKLNYRfdo$ for graphic product... ATTN...WFO...HGX...LCH... ATTN...RFC...WGRFC...NWC... LAT...LON 30879498 30749419 29699387 28759452 28799578=20 30309597=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .