Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 20 2023 17:45:07 AWUS01 KWNH 201745 FFGMPD TXZ000-202330- Mesoscale Precipitation Discussion 0199 NWS Weather Prediction Center College Park MD 144 PM EDT Thu Apr 20 2023 Areas affected...Parts of Southeastern and Eastern Texas... Concerning...Heavy rainfall...Flash flooding possible Valid 201745Z - 202330Z SUMMARY...Scattered slow-moving and potentially stationary storms with intense rainfall rates 2-2.5"/hr are possible along a convergent axis of tropical moisture streaming out of western Gulf of Mexico. DISCUSSION...Radar and satellite observations depict very small/narrow updraft cores developing near and along an axis northwest of San Antonio, Texas. Meanwhile, several boundaries can be depicted within the cloud layer ahead of the main cold front sweeping through north-central and West Texas. PWATs above 1.5" are nosing northward out the western Gulf of Mexico across South Texas and the Middle Texas Coast, with hires CAMs forecasting these values to rise above 1.75" inland across much of eastern Texas by 19z. Weak capping between 850-700 mb across southeastern TX should break by about 18z and allow for scattered to widely scattered convection to develop into stronger/broader updrafts. These cells along the southern periphery of the developing activity could anchor along an enhancement of surface layer moisture (parallel to the western Gulf coast, but about 120 miles inland at 16z) as the storms develop mesoscale cold pools. These storms will also battle between moderate (~15 kt) southeasterly surface flow and height falls upstream along with the approaching synoptic cold front leading to a westerly component in the mid-to-upper levels. Once cold pools strengthen enough by the evening hours, this should allow a necessary push to get convection to pick up east-southeastward propagation. However, in order for cold pools to reach this necessary strength, scattered 2-4" rainfall amounts are possible. 12z HREF probabilities for 3" in 3 hours (ending 21z) are 20-40% within the MPD area. This area of concern precedes the eventually activity associated with an approaching cold front to enter the area of concern after 00z. Localized rainfall rates up to 2.5"/hr are also possible within areas that receive the heaviest rainfall amounts and could lead to scattered flash flooding, particularly in urban regions. This area is experiencing soil moisture percentiles per NASA SPoRT between 30-70%, so not abnormal. Recent runs of the HRRR include 15 minute rainfall totals of 1.5"+, which if realized and convection can remain stagnant, localized 5" totals through early this evening are not out of the question. Snell ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!47QCWq_s3Tgs3vbiD_D8KY-WZ6_HlqhJQnsgYWy4jWvO4p78riiRRdRxqICgCBsUucNv= Ub7KtbjG-YPu2x__bwYmOls$ for graphic product... ATTN...WFO...CRP...EWX...FWD...HGX...SHV... ATTN...RFC...WGRFC...NWC... LAT...LON 31869533 31569454 30709489 29299622 28779734=20 29089791 30239753 31309653=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) .