Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 28 2023 01:52:39 AWUS01 KWNH 280152 FFGMPD TXZ000-280745- Mesoscale Precipitation Discussion 0364 NWS Weather Prediction Center College Park MD 951 PM EDT Sat May 27 2023 Areas affected...Big Bend to Southwest Texas... Concerning...Heavy rainfall...Flash flooding likely Valid 280150Z - 280745Z SUMMARY...Mature MCS in Big Bend likely to increase moisture flux convergence and rainfall efficiency into the early overnight.=20 Localized 2-4" totals. DISCUSSION...Fast moving linear MCS has reached the apex of the Big Bend with trailing to the Big Bend/Rio Grande Village continuing into Coahuila with tops cooling below -70C. As night falls, the LLJ is starting to accelerate (up to 25-30kts) parallel to the length of the Rio Grande, this should allow for a southeastward turn and continued propagation. However, with flux increasing, the overall depth of moisture is increasing as well.=20 Total PWats are increasing nearing 2". While the inflow will likely keep forward propagation fairly quick, rain rates of 2+"/hr are probable; sub-hourly totals of 1.25-1.5" in 15 minutes per 21z/00z are intense enough to overwhelm the lowered FFG values from the Pecos River Valley into Uvalde county where weekly precipitation anomalies are 250-400% of normal (and 3hr FFG values are generally less than 2.5"). As the complex drifts east, it moves deeper under the mid to upper level ridging in place. This will provide some anticyclonic enhanced outflow, but also slow mean steering flow, especially after 06z and generally become confluent as the propagation vectors turn southeast along the River. This may allow for longer duration of increasing rain rates and support localized spots of 3-4" through 08z. As such, flash flooding is becoming more likely though the overnight period. Confidence is a bit less than normal, given fairly wide spread in Hi-Res guidance particularly in the timing of the forward movement, still there are ample signals of high moisture flux/rainfall efficiency over wetter than normal soils to consider flash flooding likely into the early overnight along the Rio Grande Valley. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4zYmbTrc6rjG1XHmsBdLFE2enQED4wn8McQkJbbxUGSJmglWibP7sISoIYvPJQ-kYRVg= bEijWrPl2MJweuZKSK1sj9k$ for graphic product... ATTN...WFO...CRP...EWX...MAF...SJT... ATTN...RFC...WGRFC...NWC... LAT...LON 30890105 30610000 30249950 29589891 28769882=20 28189931 28150036 29190104 29650175 29900196=20 30410191 30840169=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) .