Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Feb 25 2023 03:01:27 AWUS01 KWNH 250301 FFGMPD CAZ000-250900- Mesoscale Precipitation Discussion 0076 NWS Weather Prediction Center College Park MD 1000 PM EST Fri Feb 24 2023 Areas affected...Portions of Southern California Concerning...Heavy rainfall...Flash flooding likely Valid 250300Z - 250900Z Summary...Widespread moderate to heavy rainfall will continue across portions of the Central and Southern CA coasts and into the Transverse Ranges, with rainfall rates increasing to 0.3-0.5"/hr (and locally reaching as high as 1"/hr). Isolated to scattered instances of flash flooding are likely to continue. Discussion...A deep, closed low is centered about 50 to 100 miles off the central CA coastline this evening, driving anomalous tropospheric moisture northeastward into portions of the Southern California coast and the adjacent Transverse Ranges. Rainfall totals have already reached 1-3 inches across much of the region over the past 12 hour, with localized amounts as high as 3-6 inches along the windward side of the taller peaks (per MRMS/rain gauge estimates). The current mesoscale environment is characterized by MU CAPE as high as 150 J/kg, precipitable water values of 0.7-0.9 inches (near the 90th percentile per NKX and VBG sounding climatology), and impressive 850 mb flow of 30-40 kts (near the max moving average per NKX and VBG sounding climatology). The next 6 hours or so (through 09z) may see conditions worsen as the low-level jet continues to strengthen (to perhaps as high as 40-50 kts). Rainfall rates of 0.3-0.5" will likely become more widespread over the next several hours, with rates locally approaching as high as 1"/hr along the slopes of the Transverse Ranges (as snow levels falling to around 3500 feet). The eventual passage of a cold front will gradually bring moderate to heavy rainfall to an end from west-to-east, resulting in additional localized totals of 1-3" (with the front likely reaching Los Angeles County between 06-09z). This additional rainfall over a relatively short period of 3-6 hours (on top of already saturated soils and rising streams/rivers) will likely=20 result in the continuation of isolated to scattered instances of flash flooding across portions of Southern CA, with low-lying and poor drainage areas across the Greater LA metro the most likely to experience any significant flooding impacts. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9IAbqkZPTCpCHgXJV0NOEEePzZAN9-CucLJfZqFz1UgVPNX0lHdA2o5Up8jWJk5W9C3x= R5Bdx5YUPgDbJrSwgTexWWk$ for graphic product... ATTN...WFO...LOX...SGX... ATTN...RFC...CNRFC...NWC... LAT...LON 34942032 34841970 34651917 34721878 34631841=20 34461817 34351793 34241766 34301730 34181729=20 34031744 33861732 33501717 33271761 33471807=20 33591861 33871902 34131944 34262012 34282057=20 34482067=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) .