Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 27 2025 14:22:10 AWUS01 KWNH 271422 FFGMPD TXZ000-271900- Mesoscale Precipitation Discussion 0088 NWS Weather Prediction Center College Park MD 1020 AM EDT Thu Mar 27 2025 Areas affected...Lower Rio Grande Valley Concerning...Heavy rainfall...Flash flooding possible Valid 271420Z - 271900Z SUMMARY...Some expansion of heavy showers and thunderstorms are expected through this morning and into the early afternoon hours. Heavy rainfall rates and locally slow cell-motions will foster a threat for additional flash flooding concerns. DISCUSSION...A mid-level trough continues to gradually advance east across the southern High Plains and adjacent areas of northern mainland Mexico with multiple embedded vort centers seen in GOES-E IR/WV satellite imagery ejecting out of the base of it toward the lower Rio Grande Valley. Radar imagery shows one band of convection that has slowly progressed through Deep South Texas over the last few hours, with the core of this activity now situated over far northeast Mexico. However, there is redevelopment seen farther northwest to the southeast of Laredo involving Zapata, Jim Hogg, and Starr Counties. This convection is generally forming along a weak instability gradient that is also aligned along an inverted surface trough which is gradually attaining sufficient baroclinicity to be classified as a weak stationary front. Despite rather modest instability parameters with MLCAPE values of 500 to 1000 J/kg, there will likely be some gradual recovering of instability with time across Deep South Texas to the southeast of this weak frontal zone which will strengthen the overall instability gradient. This coupled with ejecting vort energy and the left-exit region of an upper-level jet streak from northern Mexico across the lower Rio Grande Valley will likely tend to support and sustain the redeveloping areas of convective activity with some gradual expansion off to the northeast expected with time. PWs are generally in the 1.5 to 1.7 inch range across the area, and this coupled with the instability should be capable of favoring convection with 1 to 2 inch/hour rainfall rates going through the morning and early afternoon hours. The latest hires CAM guidance is handling the ongoing activity very poorly, so confidence is generally quite low, but given the latest convective trends, some additional rainfall totals going through early afternoon may reach 2 to 4 inches with isolated heavier amounts not out of the question given slow cell-motions. Given some of the heavier rainfall from overnight and early this morning, and thus the moistening up of the soil conditions, these additional rains over the next several hours may result in some additional flash flooding concerns. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7yGQbC0BOQX8nuGEbtr0eD5gL0LsuaytCRvB9lG0U3-n6-eCMJWmsg8izXHpTmssRSNH= oPC9bApWRWf4IRsWdzlWu0U$ for graphic product... ATTN...WFO...BRO...CRP... ATTN...RFC...WGRFC...NWC... LAT...LON 27619834 26959776 26359713 25829719 25959804=20 26459909 27159953 27609918=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) .