Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Feb 14 2025 02:17:15 AWUS01 KWNH 140217 FFGMPD CAZ000-141200- Mesoscale Precipitation Discussion 0036 NWS Weather Prediction Center College Park MD 916 PM EST Thu Feb 13 2025 Areas affected...Coastal Southern California...Foothills of the SIerra Concerning...Heavy rainfall...Flash flooding likely Valid 140200Z - 141200Z SUMMARY...The ongoing Atmospheric River event will continue into the early hours of Saturday, with the threat of .50-.75"+ hourly rainfall rates across portions of Southern California and into the western upslope of the Sierra. Flash flooding will remain likely across Southern California, especially across recent burn scar areas, and possible in the foothills of the Sierra. The flash flooding threat will be diminishing from west to east across Southern California after 0200 UTC as a cold front moves steadily east, but should perist to near 1200 UTC in the Sierra Foothills. DISCUSSION...The latest GOES-W satellite imagery shows the broad mid to upper level trof along the west coast pushing steadily inland. An axis of anomalous PW values..2 to 2.5+ standard deviations above the mean, and 850-700 mb moisture flux anomalies of 3 to 5+ standard deviations above the mean, will continue on the southeast side of this upper trof, along and ahead of the associated cold front pushing steadily eastward across Southern California this evening. Surface analysis at 0000 UTC indicates this front having pushed to the southeast of Santa Barbara and extending eastward just south of Sandburg and Edwards AFB.=20=20=20 There is good consensus in the latest hi res guidance on the timing of the primary heavy rain areas in the vicinity of this=20 front pushing across Southern California this evening. HREF neighborhood probabilities are high, 90%+, for hourly rain totals of .50"+/hr along and ahead of the front, but drop to generally less than 25% for 1"+/hr, reflective of the progressive nature of this front. This progression will lead to a sharp cutoff in the flash flood threat as the front passes. However, until this occurs, flash flooding will remain likely across Southern California, especially over recent burn scar regions.=20 ...Foothills of the Sierra Nevada... While the primary anomalous PW axis will remain across Southern California this evening, persistent west southwesterly low level upslope flow level will continue to impact the foothills of the Sierra into early Saturday. HREF neighborhood probabilities for ..50"+/hr rainfall amounts are not as high or continuous as areas across Southern California. but do depict potential for localized heavy amounts and the potential for flash flooding issues.=20 Simulated hi res radars do show potential for cells to be much slower moving and train in the upslope regions of the Sierra. In areas of training, additional hourly amounts of .50-.75"+ and additional totals of 2-3" are possible through early Saturday morning. =20 Oravec ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!89MFGru-sN9tQMcyudE5FAOdDpRlLChT9anMRUAZeQHCenuXZAVsnylGh7z6d0rV3Mh9= Cq58UMkl4T356xrp3V4SigM$ for graphic product... ATTN...WFO...HNX...LOX...PSR...SGX...STO...VEF... ATTN...RFC...CNRFC...NWC... LAT...LON 39932145 39242074 38191983 38101991 37181925=20 36221856 35051825 34711787 34711774 34451696=20 34351684 33951639 32951616 32321669 33011746=20 33041754 33101769 33441803 33491825 33951871=20 34411857 35511890 36741990 37352017 38572095=20 39722147=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .