Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 23 2024 18:47:18 AWUS01 KWNH 231847 FFGMPD AZZ000-UTZ000-NVZ000-CAZ000-240045- Mesoscale Precipitation Discussion 0710 NWS Weather Prediction Center College Park MD 245 PM EDT Tue Jul 23 2024 Areas affected...Central and Southern Sierra Nevada into Southern/Eastern CA...Southern NV...Central to Northwest AZ...Central/Southwest UT Concerning...Heavy rainfall...Flash flooding likely Valid 231845Z - 240045Z SUMMARY...Showers and thunderstorms will be initiating and expanding in coverage over portions of the central and southern Sierra Nevada and down through southern CA, northern AZ and into central/southwest UT. Isolated widely scattered instances of flash flooding are likely. DISCUSSION...GOES-W Day Cloud Phase satellite imagery shows the early stages of convective initiation beginning to take place over the orographically favored higher terrain of the Southwest, and over the next several hours there will be an expansion of this convection that will include some of the interior deserts. Very strong diurnal heating continues across the region with SBCAPE values now on the order of 1000 to 2000 J/kg across some of the interior deserts of southern/eastern CA and along some of the foothills/lower elevations adjacent to the Sierra Nevada. The airmass across much of the region is seasonably moist and consistent with a well-established monsoon regime. The PWs though are locally running as much as 2+ standard deviations above normal and the latest CIRA-ALPW data shows elevated moisture concentrations in the 700/500 mb and 500/300 mb layers. Some of the greatest concentration of this moisture is actually noted over far southern NV and adjacent areas of eastern CA where there is also proximity of a weak MCV. This MCV is a convective remnant from last night's monsoonal convection. Convection overall should be scattered in nature going through the afternoon hours, but will also be locally terrain-anchored. The proximity of differential heating boundaries near the terrain, and also in close proximity to the MCV where some pre-existing cloud cover exists, will facilitate the idea of seeing these locally anchored/terrain-focused cells that will then gradually advance off the terrain into the open deserts. Given the strong thermodynamic environment overall, and aid from orographics, the rainfall rates may reach 1 to 2 inches/hour with the stronger cells. Some spotty storm totals by late this afternoon may reach 2 to 4 inches. This will likely result in isolated to widely scattered instances of flash flooding. Again, the overall coverage of convection should be scattered in nature, but each cell is expected to be potentially quite impactful given the elevated rates and aforementioned slow movement. Burn scar areas along with localized slot canyons and the normally dry washes will again be most susceptible to impacts and this will include areas well removed and downstream from where the heaviest rainfall occurs. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8fAqFQZltQ-rUbIXbkPLWSpe65gWwgvojzA6ajHBXnAPNYRmOg9yLzYLo-cDJjiA8tZ1= lWV28PNnYBWugiLofCxYfe4$ for graphic product... ATTN...WFO...FGZ...HNX...LOX...PSR...REV...SGX...SLC...STO... VEF... ATTN...RFC...CBRFC...CNRFC...NWC... LAT...LON 38991160 38121114 36381147 34741051 34071104=20 34801393 34141529 32791555 32521626 32851670=20 34081713 34361794 35141867 36191859 38031997=20 38681938 37181665 36901543 37301419 38941259=20 =20=20=20=20=20=20=20=20=20=20=20=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) .