Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Feb 04 2024 04:58:48 AWUS01 KWNH 040458 FFGMPD CAZ000-041500- Mesoscale Precipitation Discussion 0045 NWS Weather Prediction Center College Park MD 1158 PM EST Sat Feb 03 2024 Areas affected...Central California Coastal Ranges/San Francisco Bay Area... Concerning...Heavy rainfall Valid 040500Z - 041500Z SUMMARY...Initial light to moderate over-running showers will give way to stronger showers due to rapidly deepening low with accelerating surface to mid-level WAA and strong moisture flux nearing the coast through early morning. Stronger orographic ascent will support .5"/hr rates with embedded convective showers capable of .75+"/hr over localized areas nearing the central CA coast around 12-15z.=20=20 DISCUSSION...GOES-W WV loop depicts a highly dynamic and rapidly evolving pattern along and east of 130W south of 40N off the Central and Southern CA coast. A mature surface cyclone is running eastward along 30N with a broadening wedge of mid to upper level a strato-cumulus with transverse banding pattern directed toward the Santa Cruz and Santa Lucia Ranges of central CA. A warm front resides under this shield parallel to the coast nudging near the coast with each hour. This wedge broadens into an anticyclonically curved cirrus shield indicative of the left entrance to a 120 to 150kt 3H jet streak. Providing a broad gradient of favorable divergent flow enhancing large scale ascent. In response, a new surface low northeast of the mature one is starting to rapidly deepen and is expected to drop to below 990mb by 12z west of the mouth of the San Francisco Bay, strengthening southwesterly flow and WAA into the coast mainly at after 12z. In the short term, isentropic ascent over the warm front will continue to provide lighter showers moistening the lower profiles over the area of concern reaching a .1 to .25"/hr over the next 3-6hrs with highest rates in the highest terrain of the Bolinas Ridge, Santa Cruz Mtns and northern portions of the Santa Lucia Range. 850mb southerly flow will strengthen to over 50kts and continue to veer aligning with 700mb flow bringing Total PWAT values over 1" into the coast by 09z and reaching 1.2" as the main core of the AR shifts in and 850mb flow reaching 70+kts bringing IVT values over 800 kg/m/s nearing the coast by 15z markedly increasing rainfall rates at/after that period. Between then, totals across the orography will be 2-3" with some lower elevations nearing 1" possibly. NASA SPoRT 10-40cm relative soil moisture values remain well above normal (70-90th percentile) but are generally above 65-70% from Monterey Bay, through the Santa Cruz peninsula into the Marin county, where greatest rain-rates/prolonged duration may result in higher than normal runoff. Still, the rates and totals may only result in minor flooding concerns through 12-15z. While an isolated flash flooding situation may occur in this last 3 hour period, the risk doesn't appear to be high enough to rise to the category of flash flooding possible for this MPD, but definitely will be setting the stage for the highest moisture flux/rainfall rates by late morning/afternoon. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6jTvz-MhvgP4vXLSU7LPTAuye79L_JLfMOf6xStQ4EwjFBTglrESxAkxHOIsuDXdknJV= bCkfdp4mxythi3RnmuOGCBY$ for graphic product... ATTN...WFO...EKA...HNX...LOX...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 39642349 39582276 39112214 38472160 37582129=20 36372087 35462099 35682146 36372201 36822214=20 37382265 37812269 38042314 38392325 38802373=20 39052385 39462386=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) .