Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 08 2023 09:31:57 AWUS01 KWNH 080931 FFGMPD CAZ000-081500- Mesoscale Precipitation Discussion 0030 NWS Weather Prediction Center College Park MD 431 AM EST Sun Jan 08 2023 Areas affected...central to southern CA coast Concerning...Heavy rainfall...Flash flooding possible Valid 080930Z - 081500Z Summary...Locally heavy rain will remain likely over portions of the central to southern CA coast through 12-15Z. Peak hourly rainfall of 0.5+ inches will be most likely in the Santa Cruz Mountains and the Santa Lucia Range where an additional 1-2 inches of rain is expected. A localized risk of flooding/debris flows will continue until about 15Z. Discussion...GOES West infrared imagery and GLM data showed an impressive burst of convection that moved across the north-central coast of CA between 06-08Z, aided by the left exit region of an upper level jet streak crossing San Francisco Bay. Surface observations from 09Z showed that the occluded/cold front has pushed just past the Bay region with a frontal band of moderate to locally heavy rain into the Santa Cruz Mountains. Recent GPS data showed precipitable water values were within 0.1" of one inch extending from Monterey Bay to Point Conception. Instability has increased over the past few hours with 100 to 500 J/kg MUCAPE from Monterey Bay, northward, via recent SPC mesoanalysis data. Meanwhile, 850 mb winds were between 60-70 kt at KMUX, tied to a low level surge of flow just ahead of the surface front. Short term forecasts from the RAP show the cold front steadily translating southward down the coast through 15Z but with weakening IVT as 850 mb winds lower to about 30 kt along the coast as the front nears Point Conception around 15Z. Prior to that time, rainfall totals of 0.5+ inches in an hour will remain possible as low level flow becomes more orthogonal to the Coastal Range, but with a relatively short duration of 1-2 hours at any given point. These locally higher rates combined with light to moderate rain over the next several hours could support another 1-2 inches of rain prior to 15Z, with a focus along the favored terrain from Monterey to Santa Barbara counties. Given ground conditions are near or at saturation, additional rainfall will support localized flooding and possible debris flows, especially if overlap of higher rain rates occurs with recent burn scar regions. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4k0J3a3Ucq5ZauQ_eHTt4ug2qi_G6db-Nj3Q1WPiGKgD7l9FPTKGpupuqICAFdGMH6QI= 3p3Eua9A0lesGFgusxut-X0$ for graphic product... ATTN...WFO...HNX...LOX...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 37532168 37342125 36822097 35962020 35451982=20 34771931 34441909 34181929 34242041 34352090=20 35302147 36382234 37272247=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) .