Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 23 2025 19:32:34 AWUS01 KWNH 231932 FFGMPD AZZ000-UTZ000-NVZ000-CAZ000-240130- Mesoscale Precipitation Discussion 0985 NWS Weather Prediction Center College Park MD 331 PM EDT Sat Aug 23 2025 Areas affected...Central to Southwest UT...Central to Northwest AZ...Southern NV...Far Eastern CA Concerning...Heavy rainfall...Flash flooding likely Valid 231930Z - 240130Z SUMMARY...Monsoonal moisture entrenched over the Southwest U.S. will support locally heavy showers and thunderstorms through this afternoon. Scattered areas of flash flooding will be likely today, and especially near and around the more sensitive slot canyon and burn scar locations. DISCUSSION...A deep layer subtropical ridge near the Four Corners region has allowed monsoonal moisture to become rather well entrenced around its western flank over the last couple of days, with PW anomalies this morning reaching as high as 2 to 3 standard deviations above normal across far eastern CA up through southern NV and into far northwest AZ and adjacent areas of central to southwest UT. The moisture is quite concentrated in the 700/300 mb layer based on the latest CIRA-ALPW data and this coupled with orographics and additional daytime heating/surface-based instability will favor expanding areas of showers and thunderstorms with elevated rainfall rates capable of reaching 1.5+ inches/hour. SBCAPE values of 1000+ J/kg are already noted over portions of central AZ and also over southern UT where there has also been recent convective development, and these values should continue to increase in the near-term. Given the influence of orographics/terrain-driven circulations and eventually convectively-driven outflow boundaries, there should be pockets of locally focused convection where some of the rainfall totals may reach as high as 2 to 4 inches. This will be supported by the anomalous moist monsoonal environment that is generally in place. These rainfall totals may result in there being enhanced runoff/debris flow concerns near any burn scar locations, and portions of northern AZ in particular are notably sensitive due to recent fire activity. Adjacent areas of southwest to central UT will also have concerns once again for slot canyon flash flooding which may be locally significant today. The flash flood threat is more conditional across southern NV and adjacent areas of far eastern CA, but in general across the MPD area, scattered areas of flash flooding are likely going through the afternoon hours as convection develops and expands in coverage. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!65ZV872x4R4Qvt_5TfR9p-kqddEwY-iXRwyh16S5PczJCf7cD-cJfgjOZNR9ot_2JdbC= eJf8ehBmU-TSd3v0mkXwugw$ for graphic product... ATTN...WFO...FGZ...PSR...SLC...VEF... ATTN...RFC...RSA...STR...NWC... LAT...LON 39341208 38941097 37831070 35911120 34661037=20 33741076 33661308 34531532 35851597 37191572=20 37961485 38631382=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .