Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Feb 05 2024 18:07:48 AWUS01 KWNH 051807 FFGMPD CAZ000-060500- Mesoscale Precipitation Discussion 0050 NWS Weather Prediction Center College Park MD 103 PM EST Mon Feb 05 2024 Areas affected...Southern California Concerning...Heavy rainfall...Flash flooding likely Valid 051800Z - 060500Z Summary...Numerous to widespread flooding impacts continue across the Transverse and Peninsular Ranges and surroundings (including much of the LA metro) with additional localized 1-2" expected through evening. Locally significant to extreme impacts remain possible across the hardest hit areas. Discussion...Moderate to heavy rainfall continues across portions of Southern California late this morning, as a gradually weakening atmospheric river has progressed very little over the past 12 hours. The nearly stationary plume of deep moisture is attributed to a longwave trough and upper low along and offshore of Northern/Central California, and a distinct dry slot is noted between the upper low and atmospheric river. The core of the AR (oriented directly into the LA basin) was nearly directly sampled this morning by the NKX sounding, which measured precipitable water values of over 1" (well above the 90th percentile and near the max moving average, per SPC sounding climatology). MRMS multi-sensor hourly rainfall totals have generally ranged from 0.2-0.4" over the past 6-12 hours from the Santa Monica Mountains eastward to the San Bernardino Mountains, with 24-hour rainfall observations generally ranging from 4-8" in the vicinity of the Transverse Ranges (including much of the LA metro area). These very wet antecedent conditions are resulting in the vast majority of the additional rainfall across the Transverse Ranges translating directly into runoff, leading to continued numerous to widespread instances of flooding with locally significant to extreme impacts expected (including extremely dangerous and life-threatening flash flooding and mudslides/landslides with potential debris flows). Additional localized totals of 1-2" are anticipated through 05z across upslope areas of the San Bernardino Mountains (closer to 1" or less in the vicinity of the LA metro), and much of that will occur over the next 3 hours or so before the plume drifts southeast into the Peninsular Ranges (mainly affecting areas north of San Diego). Most of these ranges have seen much less rainfall through this event so far (with the exception of the Santa Ana Mountains, which have picked up 3-6"), so impacts are expected to become more isolated to scattered (and more directly limited to the terrain) in the vicinity of San Diego. The peak of the rainfall rates are expected in the next 3-6 hours across the southern portions of the discussion area, and the diminishing moisture flux transport should result in rates of generally less than a quarter inch per hour beyond 00z (with lingering impacts from all of the runoff a distinct concern into the late afternoon and evening hours).=20 Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8rSA8usKlPnijNqx-NOUS05l8uahLMfJ_nhnTgOjbqVd4n0t1ZELFOj1wXrDoAablsCZ= 2nVcLQ9DtStmcJ4eFv4liDQ$ for graphic product... ATTN...WFO...HNX...LOX...SGX...VEF... ATTN...RFC...CNRFC...NWC... LAT...LON 34991861 34971797 34991748 34621689 33751644=20 33301661 32891679 32801686 32361723 32371859=20 32922000 34312047 34662040 34841975 34961916=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) .