Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 03 2025 18:41:57 AWUS01 KWNH 031841 FFGMPD AZZ000-UTZ000-NVZ000-CAZ000-040040- Mesoscale Precipitation Discussion 0352 NWS Weather Prediction Center College Park MD 240 PM EDT Tue Jun 03 2025 Areas affected...Southern and Eastern CA...Southern NV...Northwest AZ...Far Southwest UT Concerning...Heavy rainfall...Flash flooding possible Valid 031840Z - 040040Z SUMMARY...Scattered areas of showers and thunderstorms will develop this afternoon across the broader Southwest U.S. which will be capable of producing locally heavy rainfall. Given the high rainfall rate potential, isolated to scattered areas of flash flooding will be possible. DISCUSSION...An anomalously moist airmass through the vertical column has pooled across large areas of the Southwest U.S. with PW anomalies that are near or at record levels for the date. This coupled with strong diurnal heating/surface-based instability by later this afternoon should result in a favorable environment for showers and thunderstorms to initiate and gradually expand in coverage. An upper-level low is seen in WV satellite imagery dropping southeastward offshore of southern CA, and this is yielding very steep mid-level lapse rates along with divergent flow aloft around its northeast flank which will further facilitate convective development over the next several hours. The steep mid-level lapse rates coupled with the boundary layer heating should facilitate SBCAPE values reaching as high as 1000 to 2000 J/kg, with the greater CAPE fields likely focusing over northwest AZ and far southern NV. A combination of favorable thermodynamics along with localized orographics/terrain-induced circulations and even some modest shear over the region should yield scattered pulse to multi-cell thunderstorms which will be capable of producing rainfall rates of up to 1.5 inches/hour, with even some sub-hourly rates of 1 inch in 20 to 30 minutes possible. A look at the latest HREF/REFS guidance suggests some potential for 2 to 3+ inch rainfall totals where the storms become locally anchored near some of the terrain, and where any potential cell-merger activity occurs. This will allow for isolated to scattered areas of flash flooding to be possible. Some of the area burn scars will be at particular risk for impacts, along with dry washes and local slot canyon areas. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7bu_NYWF_fLMhfOJA9CCn2XRs97auo3iXgIJTXDFbIFwfiDH-HM3I2oZzWSQNmU3ggdK= pyQgv8KSZVa2R4-ubwYDFrE$ for graphic product... ATTN...WFO...FGZ...GJT...HNX...LOX...MTR...PSR...REV...SGX... SLC...VEF... ATTN...RFC...RSA...STR...NWC... LAT...LON 37651221 36921048 35121012 34211138 34271332=20 34171475 33541551 32731573 32611686 33501754=20 33991821 34441930 34672001 34892039 35482086=20 35792094 36042033 35641929 35731865 36291858=20 37401903 37631862 37011736 37561486=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) .