Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 21 2023 11:51:03 AWUS01 KWNH 211150 FFGMPD NVZ000-CAZ000-211800- Mesoscale Precipitation Discussion 0957 NWS Weather Prediction Center College Park MD 750 AM EDT Mon Aug 21 2023 Areas affected...Southeast CA Deserts...Much of Central Nevada... Concerning...Heavy rainfall...Flash flooding likely Valid 211200Z - 211800Z SUMMARY...Tail end of moisture flux band associated with Post T.C. Hilary. Additional 1-2" across areas already flooded could possibly reaggravate situations locally. DISCUSSION...GOES-W WV suite denotes Hilary has fully transitioned and melded with extratropical deep cyclone west of CA with trailing tail-end of broad warm conveyor belt denoted across S CA and NV. CIRA LPW also depicts core of moisture is starting to shift north and bifurcate through depth across the southeast deserts of CA into south-central NV. Sfc to 700mb still shows core of enhanced moisture through the Lower Colorado Valley nosing into the S NV and through central NV with .33 to .5" across the two layers (sfc-850 & 850-700) respectively. However, the 700-500 layer has enhanced drying overlaying this enhanced moisture, but a narrow band of enhanced moisture up to .5" does exist through the Imperial valley through the Mojave to west of Las Vegas. As such, a narrow overlap resulting in totals near 1.5-1.7" still exists near the CA/NV boarder centered over and west of the Spring Mountains. Winds through this area continue to be strong with 20-25kt at 850 becoming 40-50kts at 700mb, but fairly unidirectional through great depth. Even 500-300mb flow is unidirectional likely to allow this overlapping area of enhanced moisture to stream northward further into central NV throughout the remainder of the morning. While instability is very limited, there are hints of 250-500 J/kg of MUCAPE and with favorable right entrance ascent to 60-70kt 3H jet core near 120W, a few shallow but vertical cores of convection remain possible through the morning hours. Starting across the Mojave Desert currently, and streaking northward into northern Nye county and eventually toward Eureka county toward late morning/noon. Showers will likely be best enhanced along spines of the Ranges where any localized mountain circulation can enhance low level moisture flux convergence. Hi-Res CAMs continue to appear plausible with fairly good agreement in placement and timing to provide some increased confidence. As such, rates up to 1"/hr and localized spots of 2-2.5" remain possible. This alone may have resulted in possible flash flooding conditions, but given the recent heavy rainfall across the area...flash flooding is considered to be likely to reaggravate ongoing flooding across the area of concern through 18z, but diminishing with time and from south to north. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7JFouy4jxlVbtc7YFHfgNz0NS4JG08SpfohmVyA5SRlf_FwX3z-UXswrnVaHvFqMtZ7W= ztFt1GhBMfAfDQNgyx-kXXQ$ for graphic product... ATTN...WFO...LKN...REV...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 40901541 40321495 39271494 38261493 36911494=20 34911498 34431560 34901637 35941733 38621843=20 40231814 40881719=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) .