Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jan 11 2023 09:44:24 AWUS01 KWNH 110944 FFGMPD CAZ000-112100- Mesoscale Precipitation Discussion 0038 NWS Weather Prediction Center College Park MD 443 AM EST Wed Jan 11 2023 Areas affected...central/north-central CA coast Concerning...Heavy rainfall Valid 110941Z - 112100Z Summary...Rainfall intensity is forecast to increase along the north-central coast of CA through the morning with rainfall rates likely exceeding 0.5 in/hr after 18Z. Rainfall totals through 21Z are expected to range from 1-2 inches with localized amounts near 3 inches. Localized areas of renewed flooding may occur given wet antecedent conditions. Discussion...GOES West infrared satellite imagery at 0930Z showed a large cyclone centered over 1000 miles west of the Pacific Northwest with a pronounced area of colder cloud tops stretching from ~30N 145W to the northern third of the CA coastline. The elongated region of colder cloud tops was associated with an atmospheric river containing precipitable water values ranging from 1 to 1.4 inches as observed in blended TPW imagery. The axis of higher moisture was located along and ahead of a cold front, part of a broader cyclone with a surface low located near 44N 149W. A warm front extended southeastward from the triple point to roughly 300-400 miles west of San Francisco. A recent model consensus of 00Z global and recent regional guidance showed the warm front nearing the north-central CA coast around 18Z. The 850 mb front is forecast to push inland just beyond 18Z which should cause SSW low level winds to veer toward the WSW in the vicinity of San Francisco Bay and the Santa Cruz Mountains, supporting a greater orographic component to the low level flow (850 mb winds of 35-45 kt). Farther north, low level winds will have less of a westerly component, which will favor the southwest facing slopes of the Coastal Ranges from Sonoma into Mendocino and southern Humboldt counties. Portions of the region have received 4-7 inches of rain over the past 48 hours with all of coastal north-central CA experiencing 400 to over 600 percent of average rain over the past 7 days. Streams and rivers are in flood stage or running well above average according to data from USGS. Therefore, while total rainfall through 21Z should only amount to 1 to 3 inches (highest for coastal locations), localized flooding may develop due to rainfall rates of 0.5 in/hr which will become likely after roughly 18Z with rates as hich as 0.8 in/hr possibly occurring into Sonoma and Mendocino counties per recent runs of the HRRR and 00Z HREF probabilities. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6cldo6S35NYTwcR3uTL50jiG7rNbxN4Ti2Qd7FPyl4zCTQmroz382pXFGNM-oec5fNKE= 2Au7OgV-14ikPIXVCv4fIy4$ for graphic product... ATTN...WFO...EKA...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 40822367 40722343 40592336 40492326 40412308=20 40272294 40102277 39832272 39592267 39392267=20 39162265 39002261 38972249 38892234 38662229=20 38352223 37832210 37562227 37402218 37272202=20 37182173 36982168 36912185 36852209 37052253=20 37622300 38672392 39542424 40122460 40482464=20 40602456 40522429 40502409 40522401 40582394=20 40702388 40772384=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) .