Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Feb 21 2024 09:59:44 AWUS01 KWNH 210959 FFGMPD CAZ000-211530- Mesoscale Precipitation Discussion 0072 NWS Weather Prediction Center College Park MD 458 AM EST Wed Feb 21 2024 Areas affected...Transverse and Peninsular Range of Southern CA Concerning...Heavy rainfall...Flash flooding possible Valid 210955Z - 211530Z SUMMARY...Heavy showers arriving across the Transverse and Peninsular Ranges over the next several hours may result in more concerns for runoff problems with at least a localized threat for flash flooding. DISCUSSION...The latest GOES-18 IR satellite imagery shows a relatively compact shortwave trough offshore of southern CA which is advancing gradually off to the east. There is a pool of instability associated with this energy with MUCAPE values just offshore of the Transverse and Peninsular Ranges of as much as 500 to 750 J/kg, and radar imagery coupled with offshore microwave/CMORPH2 data confirms some convective elements approaching the coast with pockets of heavier rainfall rates. This energy will spread inland early this morning, and the more orographically favored terrain of Santa Barbara, Ventura, and Los Angeles County will likely tend to see the heaviest rainfall rates with this concentration of showers that arrives. Some rainfall rates may reach into the 0.50" to 0.75"/hour range, and especially considering the instability parameters that are pooling along the immediate coast. Somewhat lesser rates will tend to impact Orange and San Diego County farther south, but even here, some localized rates approaching a 0.50"/hour will be possible. There has been a fair amount of spread in the 00Z HREF guidance with the details of this energy and the additional rains that may spread inland heading through the early morning hours, but based on the latest radar/satellite trends and the recent HRRR guidance, it is expected that a new round of heavy rainfall will occur. Some of the convective showers that are offshore are also quite slow-moving, and thus as they move inland they will have the capability to to produce heavy totals. Additional rainfall amounts of as much as 1 to 3 inches will be possible through early this morning before the activity then weakens and advances off to the east. Given the very wet/sensitive antecedent conditions, a renewed threat of runoff problems will exist including at least a localized threat for flash flooding where these stronger and slower moving showers focus. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9A41O5PTNrO-1qjv47E1tM81UdJHGXhqGaHZUcNKLAWbKbaSN57wDsMTbxr5CfWSXVfE= -oQ3UJMGHIPPnF3VwptzKQQ$ for graphic product... ATTN...WFO...HNX...LOX...SGX... ATTN...RFC...CNRFC...NWC... LAT...LON 34991861 34481818 34341785 34001696 33581665=20 33121644 32761642 32531660 32591717 33221763=20 33641832 34011916 34282000 34552054 34872051=20 34981977=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) .