Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 04 2025 19:04:10 AWUS01 KWNH 041902 FFGMPD AZZ000-UTZ000-NVZ000-CAZ000-050100- Mesoscale Precipitation Discussion 0218 NWS Weather Prediction Center College Park MD 301 PM EDT Sun May 04 2025 Areas affected...Portions of Eastern CA...Northwest AZ...Southern NV Concerning...Heavy rainfall...Flash flooding possible Valid 041900Z - 050100Z SUMMARY...Scattered slow-moving showers and thunderstorms across portions of eastern CA, northwest AZ and southern NV today will pose a concern for isolated pockets of flash flooding. DISCUSSION...The midday GOES-W WV suite shows a rather anomalous deep layer trough/closed over the Southwest U.S. which is forecast to move very slowly off to the east this afternoon. Cold 700/500 mb temperatures are promoting steeper mid-level lapse rates and this coupled with strong boundary layer heating via solar insolation is already contributing to MLCAPE values of 500 to 1000 J/kg. GOES-W visible satellite imagery meanwhile already shows areas of shower and thunderstorm activity developing and expanding over some of the higher terrain and adjacent deserts with some of the more notable cells situated over northwest AZ and edging into southern NV around the northeast flank of the mid-level closed low. Somewhat stronger southeast flow/shear across these areas is seen in the latest RAP analysis, and these stronger wind fields may tend to promote somewhat strong cellular organization. The PW environment for this time of the year is rather anomalous with PWs of locally 0.7 to 0.9 inches and this is 2 to 3 standard deviations above normal. Much of the moisture concentration is in the mid-levels of the column, but with the available instability and persistence of these convective cells, there may be some convective cells that are capable of producing rainfall rates of up to 1.0 to 1.25 inches/hour. Much of this rain could fall in as little as 30 minutes with the stronger and more organized cells. The 12Z HREF guidance led especially by the NAM-conest supports these rainfall rates, with some storm total potential of up to 2 inches going through this afternoon. As a result, a few isolated areas of runoff concerns and flash flooding cannot be ruled out. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7jsiFueUTM6zjTVBmvw0DaP6LwTHPxG1dHOmvlEnixt8AkRL0OXuFNUj85eqFLqLP1Sq= A56ADuquhbcmY7-hTskCEiQ$ for graphic product... ATTN...WFO...FGZ...PSR...SGX...SLC...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 37331443 36921363 35781303 34501328 33751401=20 33401505 33331636 33991687 34581624 35501580=20 36381593 37121557=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) .