Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 21 2024 22:27:30 AWUS01 KWNH 212227 FFGMPD CAZ000-ORZ000-220910- Mesoscale Precipitation Discussion 0017 NWS Weather Prediction Center College Park MD 526 PM EST Sun Jan 21 2024 Areas affected...central to northern CA into far southwestern OR Concerning...Heavy rainfall...Flash flooding possible Valid 212225Z - 220910Z Summary...Rainfall intensity will increase across northern CA this evening, expanding to the central coast later tonight. Peak rainfall rates of 0.5 to 1.0 in/hr are expected at times along with 2-4 inches of rain for portions of northern CA through 09Z. Discussion...Looping water vapor imagery (6.9 micron channel) through 2130Z from GOES West showed a strengthening shortwave over the Pacific near 130W, tracking toward the east. The shortwave was embedded within a longwave trough which was amplifying, in part due to an impressive 200 kt upper level jet arcing zonally across the east-central Pacific before curving anticyclonically just west of the southern CA coast. Infrared satellite and regional radar imagery showed a band of low level warm air advection induced showers reaching the northern CA and southern OR coast, ahead of a surface occluded front analyzed roughly 200 miles offshore. A broad region of PWATs greater than 1 inch was observed via blended TPW imagery and RAP analysis data, streaming toward the CA coast. As the mid to upper level trough continues to amplify and approach the West Coast tonight, steepening 700-500 mb lapse rates of 6.5 to 7.5 C/km are expected to support MUCAPE values up to 500 J/kg along the northern CA coast, mainly north from Sonoma County. PWAT values will increase as well with RAP forecast values maximizing near 1 inch for the northern CA coast and up to 1.2 inches from San Francisco Bay to Point Conception. 850 mb winds from the SSW to SW ranging from 30 to over 50 kt (highest near the CA/OR border) will translate into a broad region of 250-500 kg/m/s IVT from the OR coast to near Point Conception over the next 12 hours. Given the forecasts of shear and instability along and just offshore the northern CA coast, quasi-organized cells will be possible with high rainfall rates (0.5 to 1.0 in/hr). Into the Sacramento Valley, poor low to mid-level lapse rates should limit instability to 100 or 200 J/kg at most, decreasing the likelihood of seeing 0.5+ in/hr rates, though quasi-organized cells and training could still support these higher rates. Expect a transition to an increasing coverage of moderate to heavy rain in the 00Z-03Z window across the northern CA coast into the Klamath and Cascade Mountains. 2 to 4 inches of rain is expected through 09Z for portions of the northern CA coast into the Sierra Nevada. With time, areas of heavier rain should begin to move southward down the coast as the frontal system nears, with potential for 0.5+ in/hr rates into the Santa Lucia Range in the 06-09Z window. Much of the region has seen above average rainfall over the past 2 weeks, but more notably, in the past 72 hours, increasing potential for flooding from additional rainfall. Areas of flooding will be possible tonight, especially in urban areas or other locations of poor drainage. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8PV4zjnzV7xUEEpV0OHjrlwF-5r0Cqkh3XHtGgWz9-jf02qzGRiVsIlHQuD7UM1rQuCP= lyh_hCtnc1XexYNDE1bOcuo$ for graphic product... ATTN...WFO...EKA...LOX...MFR...MTR...REV...STO... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 42852453 42792409 42602380 42312374 41972349=20 41832340 41722340 41612341 41472332 41342323=20 41252310 41192291 41212277 41232269 41272257=20 41322248 41392232 41422227 41452218 41462209=20 41422202 41332197 41212191 41152180 41022173=20 40642127 40072098 39332056 39102053 38842061=20 38542090 38382112 38302130 38252159 38312175=20 38292204 38092220 37862218 37672206 37282184=20 36962165 36502139 36092093 35382067 35242071=20 35092086 35052112 35272152 35902216 37162318=20 38012379 39652466 40672486 41932496 42712481=20 =20=20=20=20=20=20=20=20=20=20=20=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) .