Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 23 2023 09:06:12 AWUS01 KWNH 230906 FFGMPD TXZ000-NMZ000-231500- Mesoscale Precipitation Discussion 0964 NWS Weather Prediction Center College Park MD 504 AM EDT Wed Aug 23 2023 Areas affected...West Texas Concerning...Heavy rainfall...Flash flooding possible Valid 230900Z - 231500Z Summary...Locally heavy rainfall (with rates of 1-2"/hr) in association with Tropical Depression Harold is expected to lead to localized short-term totals of 2-4". Isolated to widely scattered instances of flash flooding are possible. Discussion...Tropical Depression Harold continues to trak west-northwestward through northeastern Mexico, now entering the higher terrain of the Chihuahuan Desert. Deep persistent convection (per GOES-East infrared imagery) has been ongoing to the north-northwest of the center of Harold, and this convection is beginning to move into the West Texas portions of the Chihuahuan Desert. Rainfall rates in association with this deep convection are likely on the order of 1-2"/hr, as radar coverage across this region of West Texas is poor (even when the currently down KMID radar is operating). The MRMS RQI (radar quality index) for the Texas Big Bend and northward into the Trans-Pecos is near 0%, indicating unreliable radar observations (with the nearest beams scanning far too high up in the troposphere to be of reliable use for precipitation estimates). Despite the poor radar coverage and quality, a period of locally heavy rainfall is expected from morning to mid-day across much of West Texas, as the center of Harold continues to track northwestward (at near 12 kts, per the latest 09z WPC advisory). Hi-res model guidance (including the 00z HREF and more recent HRRR runs) is in rather good agreement concerning expected rainfall, suggesting localized totals of 2-4" through 15z. The most favored cooridor for these higher amounts extends across much of Brewster into western Terrell, southern Pecos and Reeves, and eastern Jeff Davis and Presidio counties. The 00z HREF 40-km neighborhood probabilities for 2" and 3" thresholds are between 30-50% and 15-25%, respectively, and the HRRR runs since 00z depict the heaviest totals in these areas as well (consistent with observational trends in the deep convective activity). The bulk of this rainfall is expected to occur over a 3-hr period, with associated Flash Flood Guidance (FFG) generally ranging from 2-4". Since this would require the precipitation to fall in the most hydrologically sensitive spots (which is primarily in the vicinty of Fort Davis and points northwestward into far West TX) to exceed FFG, isolated to widely scattered instances of flash flooding are considered possible. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-NUxZ62YebqMcc8qP7ZymSx4XBmC6dCnZK6_S3LLuiHEhjWm83aFQip4OR88u1lXNz96= 8S0It_3qtZVntoJlfZexebg$ for graphic product... ATTN...WFO...EPZ...EWX...MAF... ATTN...RFC...WGRFC...NWC... LAT...LON 32330552 32120432 31660331 30620196 29400140=20 28090174 28390315 29210475 29930592 30910697=20 32040674=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) .