Subj : MESO: Heavy Rain/Flood CA To : All From : Mike Powell Date : Sun Mar 31 2024 08:46:00 AWUS01 KWNH 311102 FFGMPD CAZ000-311700- Mesoscale Precipitation Discussion 0119 NWS Weather Prediction Center College Park MD 701 AM EDT Sun Mar 31 2024 Areas affected...Southern California... Concerning...Heavy rainfall...Flash flooding possible Valid 311100Z - 311700Z SUMMARY...Potential for slow, perhaps stationary widely scattered shallow thunderstorms with capability of 1-1.5"/hr totals will continue to pose focused, highly localized flash flooding potential this morning. DISCUSSION...GOES-W WV and EIR suite depicts the seasonally anomalous deep closed low (2-3 std dev) continues to wobble southwest of the Channel Islands. The core vorticity center continues to be well defined along the south-southwest edge of the larger circulation starting to press eastward. This, in combination with exiting subtropical jet streak through the Desert Southwest continues to provide a favorable ascent pattern aloft across the California Bight into Southern California; while in the lowest levels south to southeasterly confluent flow enhanced by topographic channeling of the flow along the coastal region continues to provide ample but focused moisture convergence from the Santa Barbara coast toward NW LA county coast. WV/EIR loop also depicts the old occlusion boundary is starting to sag southward across central CA with the nose of a jet streak starting to press southwestward out of the central Sierra. This will further accelerate low level winds and moisture convergence but with limited mid-level steering given the axis of the mid-level trof lies across the northern channel islands through the southern Sierra Nevada/Tehachapi Range. CIRA LPW denotes modest remaining moisture along this low level confluence axis with Sfc-700mb moisture near .5-.7", combined with steep/cold mid-level lapse rates (likely to further steepen with DPVA associated with rounding shortwave); instability of 750+ J/kg will continue to support stronger updrafts capable of vertical moisture loading with up to 1.5-1.75"/hr. This may result in a spot or two of 1-2" totals across SE Santa Barbara, Ventura into W LA county where cells may be near stationary at apex of the mid-level pivot/trof aloft. Further south coverage should be greater in the southwesterly flow regime aloft from LA to San Diego county, cell motions may limit duration a bit...but the risk for intense cores still will result in potential for localized flash flooding concerns through the morning into the evening. Gallina ATTN...WFO...LOX...SGX... ATTN...RFC...CNRFC...NWC... LAT...LON 34862024 34581868 34261755 33301680 32521680 32541787 33071932 33602006 34182049 34672068 = = = --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .