Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 24 2023 18:41:16 AWUS01 KWNH 241841 FFGMPD COZ000-WYZ000-AZZ000-UTZ000-250035- Mesoscale Precipitation Discussion 0970 NWS Weather Prediction Center College Park MD 240 PM EDT Thu Aug 24 2023 Areas affected...southern/eastern UT into western/central CO and far southern WY Concerning...Heavy rainfall...Flash flooding possible Valid 241838Z - 250035Z SUMMARY...Isolated to widely scattered areas of flash flooding will be possible through the afternoon into the early evening from southern/eastern UT into western/central CO and far southern WY. Rainfall rates of 1-2 inches in an hour or less will be possible. DISCUSSION...Water vapor imagery at 18Z showed a well defined mid to upper-level vorticity over the eastern AZ/UT border, drifting northward. Highly anomalous moisture was in place across portions of the West with 12Z soundings from SLC and GJT showing 1.15 inch precipitable water values, standardized anomalies of +2 to +3 for late August. Using 850-300 mb layer winds as a proxy for storm motions, much of UT should experience steering flow of less than 10 kt, but extensive cloud cover has been limiting surface heating and instability. Farther east into western and northern CO, reduced cloud cover has allowed for better heating at the surface and early development of diurnally-driven showers and thunderstorms from northwestern NM into portions of the CO Rockies. While instability may become more favorable over CO and portions of the region receiving better insolation, estimated storm motions are higher from the Four Corners region into central CO at 10-20 kt, which may limit the flash flood threat. Continued daytime heating is expected to support MLCAPE values between 500 and ~1000 J/kg by 21/22Z from eastern UT into western CO, west of the Continental Divide. Better synoptic scale lift ahead of the northward drifting vorticity max will exist from central/eastern UT into western CO, but coverage of thunderstorms is a bit uncertain given cloud cover in place as of 18Z. Farther east into CO and far southern WY, thunderstorm coverage should be more numerous with potential for repeating rounds with the environment supportive of 1 to 2 inches of rain in an hour or even less than an hour where slower movement or short-term training occurs. Areas of isolated to widely scattered flash flooding will be possible through at least 01Z with overlap of heavy rain enhancing the flash flood risk over vulnerable slot canyons, dry washes or otherwise sensitive locations. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Rp5eP9QYMqzV5lfAMUmrO64nVxnaxZdOmBXu_ajWNgZyf7uqb9tdmJcGCBKQfkgHa9A= E3yJw5Mppp_FF4najFmbSGw$ for graphic product... ATTN...WFO...BOU...CYS...FGZ...GJT...PUB...SLC...VEF... ATTN...RFC...ABRFC...CBRFC...MBRFC...NWC... LAT...LON 41620595 41350535 40540530 39380605 38100691=20 37570813 37360969 37221072 37061172 36921244=20 37011326 37281355 37811342 38751272 39451198=20 40031101 39981051 39820987 39830924 40080856=20 40640766 41190709 41530656=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) .