Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 01 2023 17:42:13 AWUS01 KWNH 011742 FFGMPD AZZ000-NVZ000-CAZ000-012330- Mesoscale Precipitation Discussion 1018 NWS Weather Prediction Center College Park MD 141 PM EDT Fri Sep 01 2023 Areas affected...Lower Colorado River Valley... Concerning...Heavy rainfall...Flash flooding likely Valid 011745Z - 012330Z SUMMARY... Thunderstorms developing along the Gulf of California are growing upscale into southwest Arizona. Additional showers and thunderstorms will develop over southeast California, with cell mergers likely into this afternoon, resulting in localized flash flooding. DISCUSSION... A deep longwave trough is rapidly digging southward down the California coast. GOES-W WV suite denotes a compact mesoscale shortwave trough over the northern Gulf of California lifting northward causing a cluster of strong thunderstorms to develop from the Gulf of California northward into extreme southern Arizona. These two features are likely to merge near/over the Lower Colorado River Valley, causing strong thunderstorms to develop with daytime heating. The storms will be capable of heavy rainfall, which is likely to result in flash flooding over the desert. PWATs of 1.5 to 2 inches being advected north out of the Gulf of California are contributing to PWAT anomalies around 2.5 sigma above normal in this area. Solid insolation this morning has resulted in increasingly unstable environment with MLCAPEs of 1500-2000 J/kg available for stronger updrafts and moisture loading into the downdrafts. This should support widespread shower and thunderstorm development across this region, especially as the two features merge. Convection may initially develop along the mountains associated with the trough, but are likely to propagate northeastward following the moisture influx and instability which will rapidly increase through the late morning with daytime heating. Resultant flash flooding is most likely in any urban areas impacted, such as Lake Havasu and Yuma as well as across impervious ground surfaces, allowing increased runoff and likely scattered incidents of flash flooding, given suggestion of 1-1.25" totals in 15-30 minutes (as suggested by the HRRR). =20 Wegman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Ud6tV2VPk0Qy_EnYSM32zLDNAFguEN4Jbce3YklLmSgUr9vJhRFSDJHgiIVBziPAyG7= -slCmtmUlaQMdJJsIiCL4V4$ for graphic product... ATTN...WFO...FGZ...PSR...SGX...TWC...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 35331547 35261418 34291306 33001208 32221154=20 31591171 32401458 32591603 34051647=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) .