Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 23 2024 02:20:35 AWUS01 KWNH 230220 FFGMPD AZZ000-NVZ000-CAZ000-230800- Mesoscale Precipitation Discussion 0702 NWS Weather Prediction Center College Park MD 1020 PM EDT Mon Jul 22 2024 Areas affected...Portions of the low and high deserts of NV, CA, and AZ Concerning...Heavy rainfall...Flash flooding possible Valid 230219Z - 230800Z Summary...Slow moving showers and thunderstorms will drift southward into the overnight hours. Rainfall rates of 0.5"-1"/hr are possible in the stronger thunderstorms, which could produce instances of flash flooding. Discussion...The GOES-W WV imagery tonight indicates a weak mid-level shortwave trough diving southward from the southern Great Basin into the High Deserts near Las Vegas, NV. This is manifesting with increasing coverage of slow moving convection across the region, as this ascent acts into favorable thermodynamics. Regional PWs as measured by GPS are 1.1-1.3 inches, and measured at 1.18 inches at KVEF on the 00Z U/A sounding, above the 90th percentile for the date. This moist column is accompanied by a ribbon of elevated SBCAPE reaching 1500 J/kg. Together, these are fueling thunderstorms which have radar estimated rain rates of more than 2"/hr from KESX WSR-88D. As the mid-level trough continues to dig southward, it will likely drive additional convective development for several more hours until nocturnal overturning can stabilize the environment. Although the recent HRRR is very scattered with its coverage, its evolution of a few rounds of thunderstorms dropping southward seems reasonable. This is especially true as modest 20kts of bulk shear may help organize a few storms beyond pulse-type, but even where convection remains of the pulse variety, outflows and storm mergers will likely induce additional development as weak southerly 850mb inflow maintains elevated thermodynamics across the High and Low deserts. Mean cloud layer wind of just around 5 kts will support generally slow motions, with rain rates above 0.5"/hr, and while any organized clusters may become more outflow dominated and move slightly faster to the south, these could also contain heavier rain rates approaching 1"/hr as reflected by low HREF neighborhood probabilities. The scattered coverage in the CAMs is limiting HREF probabilities for total rainfall, but a few areas could reach 0.5-1" of rainfall, with isolated higher totals possible. These intense rain rates will move across areas with low 1-hr FFG of only 0.5-1", and although rainfall exceeding these amounts is likely to be isolated in coverage, the rates could still lead to rapid runoff in the sensitive soil types. This suggests at least isolated instances of flash flooding are possible tonight. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7UYCB81vZA-uetgR7hTGo5Uvw60Pdh7317biN2cRDBE6s4mXpbgyvv4xTxYGvypw3-rg= d7iUyplrFb-ok5bZA8Ejlvk$ for graphic product... ATTN...WFO...FGZ...PSR...VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 36851522 36721455 36301373 35711330 34531301=20 33921310 33411378 33291452 33461518 33931599=20 34641641 35221638 36151626 36791570=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) .