Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 13 2023 16:21:05 AWUS01 KWNH 131620 FFGMPD LAZ000-TXZ000-132130- Mesoscale Precipitation Discussion 0288 NWS Weather Prediction Center College Park MD 1220 PM EDT Sat May 13 2023 Areas affected...middle/upper TX Coastal Plain into eastern TX Concerning...Heavy rainfall...Flash flooding possible Valid 131619Z - 132130Z SUMMARY...A threat of flash flooding will continue across portions of the middle/upper TX Coastal Plain into eastern TX into the afternoon. Rainfall rates of 1-2 in/hr but locally 2+ in/hr will be possible along with localized totals of 2-4 inches. DISCUSSION...Visible satellite and regional radar imagery through 1530Z identified an elongated outflow boundary stretching southward across eastern TX to a point just north of Matagorda Bay, where it joined another outflow boundary stretching southeastward/southward into the western Gulf of Mexico. Meanwhile, an MCV was located just inland of Aransas Bay, moving to the north. Well defined cloud streets in eastern TX and western LA corresponded with uncapped MLCAPE of 1500 to over 2000 J/kg via the 15Z SPC mesoanalysis, which also extended southwestward to the middle TX coast, ahead of the outflow boundary. Precipitable water values across the region of 1.5 to 1.7 inches will continue to carry the potential for high rain rates into the afternoon although some questions remain with the exact evolution moving forward. While CAMs are struggling to handle the surface boundaries correctly, it seems localized flash flooding will remain a concern for portions of the Coastal Plain into eastern TX. 0-1 km flow was 20-30 kt oriented orthogonal to the coast and the portion of the outflow boundary west of Galveston Bay, supporting overrunning convection. While recent shower activity to the west and north of Houston has been disorganized and not much of a concern regarding flash flooding, just ahead of the eastward advancing outflow boundary moving up the middle TX coast, slow moving/training cores of heavy rain will remain possible across inland locations with rainfall rates of 1-2 in/hr as the outflow continues to advance toward Galveston Bay, although some slowing of the boundary will be possible after 18Z. Across eastern TX, there are some concerns with convective development within the unstable airmass along and east of the well-defined outflow boundary which has slowed recently with movement at 10-15 kt. Low level and deeper-layer winds are from the south to south-southeast, mostly parallel to the boundary and with similar magnitude from 925 to 400 mb. If storms are able to materialize and gain sufficient coverage, there could be some training along a south to north axis, at least initially, before outflow potentially takes over given some dry low to mid level air noted in the 12Z LCH and SHV soundings. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8e9KnXjs8T0lzZgOhmVka-q0fKLdZW0Wrxe8ojf3eDJEGHcoPtEQ-ocwyM1Mx6pL7diM= -NPW9WyMDyzGU6l231jE5z8$ for graphic product... ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 33689529 33639461 33079430 32139398 31139386=20 29889406 29309464 28569568 28349633 29139690=20 29869659 30479603 31119568 31869553 32869554=20 33279549=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) .