Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Dec 21 2023 21:31:21 AWUS01 KWNH 212131 FFGMPD CAZ000-220330- Mesoscale Precipitation Discussion 1213 NWS Weather Prediction Center College Park MD 430 PM EST Thu Dec 21 2023 Areas affected...Portions of the Central and Southern California Coast Concerning...Heavy rainfall...Flash flooding likely Valid 212130Z - 220330Z SUMMARY...The flash flooding threat continues along portions of the central and southern California coast. The heaviest rain will shift west, resulting in diminishing rainfall rates from east to west through this afternoon. DISCUSSION...Heavy rainfall continued this morning primarily through the Santa Barbara area, where considerable flash flooding is underway, including flooding of homes and businesses in the Santa Barbara area. The corridor of heaviest rain remains near Santa Barbara, and is likely to persist over the next several hours as it only slowly drifts westward. 6 hourly rainfall totals of 2 to 4 inches have been reported in and around Santa Barbara, with considerably lighter amounts both east and west, showing how narrow a corridor of heavy rain this has been so far. The upper level shortwave forcing supporting the heaviest rainfall and circulating around the broader upper low is moving offshore to the west. MUCAPE values have only diminished to between 250 and 500 J/kg. CAMs guidance is in good agreement that on the whole, the heaviest rainfall within the corridor should gradually diminish with time. All of these factors are likely to result in more intermittent periods of heavy rain with rates up to an inch per hour, but the training and painfully slow broad movement of the heavy rain corridor will keep the flash flooding threat in the likely category through the afternoon, particularly around Santa Barbara. As the corridor of heaviest rain shifts west late this afternoon and evening, increasing easterly/offshore/downslope flow should result in a sharp cutoff on the eastern side of the precipitation shield. The upper level low driving all this rainfall is moving southeastward well off the coast of Mexico, which will result in a reorientation of the rain bands from the current SSE-NNW to SE-NW this evening, and eventually E to W by late tonight. This in turn will result in diminishing rainfall for areas further north into Monterey and SLO Counties, though coastal sections of those counties may continue to see heavy rain well into the late afternoon. However, this same trend may allow bands of heavy rain to impact the remainder of the CA coast down to the Mexico border late tonight. Wegman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9kAJBZn6Hwr2aOcMYeAk8fw2jEtqqKqfhf24diDYGBB-K8BvKFHMOWR4wEQr0NakLAXF= gpoM9Bbn7AKKKm6Cbn6urV4$ for graphic product... ATTN...WFO...HNX...LOX...MTR... ATTN...RFC...CNRFC...NWC... LAT...LON 36282129 36192061 36102037 36092022 35952002=20 35571954 35151904 34831880 34461876 34021906=20 34351958 34412052 35082071 35532122 36072166=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .