Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 01 2023 04:15:30 AWUS01 KWNH 010415 FFGMPD AZZ000-UTZ000-NVZ000-CAZ000-010915- Mesoscale Precipitation Discussion 1015 NWS Weather Prediction Center College Park MD 1214 AM EDT Fri Sep 01 2023 Areas affected...southern to northwestern AZ into southwestern UT and southeastern NV Concerning...Heavy rainfall...Flash flooding possible Valid 010409Z - 010915Z Summary...Areas of localized to widely scattered flash flooding will be possible across southern to northwestern AZ into southeastern NV and southwestern UT overnight. Thunderstorms will carry the potential for rainfall rates of 1-2 inches in 30-60 minutes. Discussion...Several areas of thunderstorms were observed across the Desert Southwest as of 0345Z via infrared satellite and regional radar imagery. A mid to upper level ridge centered over east-central NM and troughing along/offshore of the West Coast was allowing for southerly flow through AZ along with steadily increasing moisture observed since 12Z Thursday. Moisture anomalies were greatest over the Colorado River Valley with 22Z and 00Z soundings at 1Y7 and VEF (respectively) showing precipitable water values well above the 90th percentile via the SPC sounding climatology page. 00Z soundings from TUS, PSR, FGZ and VEF also showed up to 1000 J/kg MLCAPE but with significant dry layers in the 0-10 kft AGL layer, supporting outflow dominant storms/clusters. One thunderstorm cluster over southern AZ was associated with a northward moving outflow boundary that crossed through the Phoenix metro around 0330Z and another translating north from southern UT. Despite cooling surface temperatures into the night, fairly steep mid-level lapse rates and continued advection of low to mid-level moisture will likely maintain sufficient instability overnight to support additional rounds of nocturnal convection. Expectations are for thunderstorms to expand northward from the ongoing cluster over Maricopa and Pinal counties, with localized cell development in advance of the outflow boundary. Repeating rounds of thunderstorms will be possible despite a progressive movement toward the north. For locations farther north, relatively stronger 700 mb flow near 20 kt will allow for repeating and brief training of thunderstorms from the southern CA/NV border toward the northeast. T he environment will be supportive of 1-2 inches of rain in 30-60 minutes with stronger cores and/or any training that is able to materialize. A few areas of flash flooding will be possible as a result, especially if overlap of heavy rain occurs with burn scars or low water crossings/creeks/normally dry washes. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!47XOGnCTS4lXblDB5c3Xk6dFxe8kpiLFKmkHR-gdJzFWLiNKOUBXLJiFvUXsBHGmiJfV= 4sDqU_NFkItT6DnQIE_92FE$ for graphic product... ATTN...WFO...FGZ...PSR...SLC...TWC...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 38881259 38611182 37401178 36171160 34891140=20 34061113 33561098 32971090 32321086 31861089=20 31521101 31511135 31771243 32491306 33591388=20 35461498 37221478 38311360=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) .