Subj : MESO: Heavy rain/flooding To : All From : Mike Powell Date : Sat Feb 10 2024 08:47:00 AWUS01 KWNH 101042 FFGMPD LAZ000-TXZ000-101641- Mesoscale Precipitation Discussion 0055 NWS Weather Prediction Center College Park MD 542 AM EST Sat Feb 10 2024 Areas affected...portions of southeast TX & western LA Concerning...Heavy rainfall...Flash flooding possible Valid 101041Z - 101641Z Summary...A low-level convergence zone is expected to gather an increasing amount of thunderstorm activity through the morning hours. Hourly rain totals to 2" with local amounts to 4" are possible. Discussion...A shortwave moving near El Paso has been enhancing outflow aloft across much of central and eastern TX and slowly eroding CIN. Precipitable water values near the TX coast have risen into the 1.5-1.75" range per GPS data. MU/ML CAPE has been more or less stable near 250 J/kg on SPC mesoanalyses. A low-level convergence zone, occasionally showing up in the surface pattern but more evident at 925 hPa and 850 hPa, has been moving little near the Middle and Upper TX coasts and across western LA within the warm sector of a low over TX, which helped focus a band of showers hours ahead of what was suggested by the 00z HREF. Around 3 a.m. CST, there was a spike in hourly rain totals up to 1.5", also earlier/more than anticipated by the guidance, from the Galveston/Harris County border into southeast Liberty County. Various model fields suggest that instability will be stable or slowly increase initially, before going upward faster later this morning near the southern end of the low-level convergence zone either due to daytime heating or the approaching shortwave. A boundary itself may shift slightly northward. The past few HREF runs have been slowly trending to a wetter signal across this region, focusing more on this convergence zone and less on the front to the north. As the shortwave near westernmost TX approaches, the expectation is for convective coverage to increase near the convergence zone, particularly after 13z per the 00z/06z HREF guidance is to be believed. The 00z ARW appears best placed with what's expected, based on what's occurred thus far, though its amounts could be a little light. Hourly rain totals are expected to peak in the 2" range, with local amounts to 4" being possible, which would exceed the three hour flash flood guidance. Any heavy rain-related issues would be isolated to widely scattered, with urban areas most sensitive. Roth/Asherman ATTN...WFO...HGX...LCH...SHV... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 31799320 31209252 30029415 28999604 29509646 30789509 = = = --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .