Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 08 2023 03:34:51 AWUS01 KWNH 080334 FFGMPD CAZ000-080930- Mesoscale Precipitation Discussion 0028 NWS Weather Prediction Center College Park MD 1033 PM EST Sat Jan 07 2023 Areas affected...central to northern CA Concerning...Heavy rainfall...Flash flooding possible Valid 080331Z - 080930Z Summary...Periods of heavy rain will spread across portions of northern to central CA over the next 6 hours. Rainfall rates may occasionally exceed 0.5 inches in several locations across CA but the focus will be south of Monterey Bay where hourly totals up to an inch will be possible. Given antecedent wet conditions and burn scar locations, localized flooding and/or debris flows may occur. Discussion...Recent water vapor imagery from GOES West showed a negatively tilted mid-upper level trough axis approaching the West Coast while 03Z infrared imagery helped place a related occluded cyclone over the eastern Pacific with scattered pockets of colder cloud tops noted between the occluded/cold front and central CA. GPS observations along the coast showed values near 1 inch from Monterey Bay to just north of San Francisco Bay but instability along the coast to the inland Valley was lacking. VAD wind plots and RAP analysis data showed 850 mb winds from the south between 40-50 kt along the coast helping support occasional bursts of heavy rain with a band of higher reflectivity ongoing into northern San Luis Obispo County. 700 mb winds were locally in excess of 50 kt for northern portions of CA. As the upper trough nears the CA over the next few hours, the occluded/cold front should reach the coast in the 06Z-09Z time frame along with increasing diffluence aloft. 700-500 mb lapse rates will also increase over the next 6 hours with values of 7 to 8 C/km spreading into central CA as lower mid-level heights advance eastward (via recent RAP forecasts). This will help to increase instability to a few hundred J/kg from the Coastal Ranges to some inland locations of the Sacramento and San Joaquin Valleys. With the approach of the surface front and upper trough aloft, 850 mb winds will veer along the coast (more orthogonal to the axis of terrain) with values exceeding 50 kt at times. While precipitable water values are not forecast to get much above 1 inch along the coast, the increasingly favorable orientation of the low level flow into the Santa Lucia Range combined with diffluence aloft is expected to support rainfall rates over 0.5 inches at times, perhaps as high as 1 inch. The plume of higher IVT will begin to shift southward along the coast beyond 09Z as the cold front continues to advance inland. Total rainfall over the next 6 hours should range from 1-2 inches, but values over 3 inches will be possible across the Santa Lucia Range where recent burn scars may increase the risk of flooding/debris flows given wet antecedent conditions. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Ai7O5uOPMMe9_qzSvnLEz-BBDvjBQroiOib__69HuXfxT2zi8QV73Z88QPL8KhA3zxb= Gv2DNwDijuuhKrRHC25mqGg$ for graphic product... ATTN...WFO...EKA...HNX...LOX...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 40972266 40602176 39472079 38002026 37202083=20 36622080 35622015 34842056 34992128 35772215=20 37242290 38932430 40302463 40802383=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) .