Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 20 2024 17:05:28 AWUS01 KWNH 201705 FFGMPD CAZ000-ORZ000-210500- Mesoscale Precipitation Discussion 0016 NWS Weather Prediction Center College Park MD 1204 PM EST Sat Jan 20 2024 Areas affected...northern CA into southwestern OR Concerning...Heavy rainfall...Flash flooding possible Valid 201703Z - 210500Z Summary...Heavy rainfall will gradually shift northward from northern California into southwestern Oregon today. Peak rainfall rates over 0.5 in/hr and 12 hour totals of 2-4 inches are expected which may lead to localized areas of flooding. Discussion...1630Z water vapor imagery (6.9 micron channel) from GOES West showed a closed low centered near 42.5N 125.1W, moving off toward the NNE. Areas of heavy rain have been observed to the southeast of the mid to upper level low across northern CA since ~11Z with the heaviest rainfall focusing across Humboldt County. Recent RAWS and Wunderground observations have shown hourly rainfall in the 0.50 to 0.75 inch range within the King Range and 6 hour totals in the 2-3 inch range. This area of northern CA was located beneath the left exit region of a subtle jet streak aloft (currently crossing the coast), measuring at least 60-70 kt per GOES West DMVs near 300 mb and beneath a region of maximized diffluence aloft. 850 mb winds per the KBHX VAD wind plot had been 50-60 kt from the SSE but have since veered to SSW and weakened into the 40-50 kt range as the corridor of stronger 850 mb winds has shifted to the far northern CA/southern OR coast with the closed low movement. Precipitable water values were measured by recent GPS and blended TPW data to be 0.8 inches along the coast to just over 1 inch offshore the OR/CA coasts. Short term RAP guidance shows the mid to upper level low continuing toward the NNE while weakening through 00Z. This movement will allow low level winds to continue to veer toward the SSW and SW through the day, promoting more of an onshore component to the winds into Del Norte and Curry counties. 850 mb winds are expected to maximize in the 40-50 kt range for these northern locations and peak IVT values will remain steady in the 400-500 kg/m/s range after initial weakening this morning in the vicinity of Cape Mendocino. Southwest facing slopes of the Coastal Ranges are expected to see several hours with steady hourly rainfall in the 0.25 to 0.50 inch range over the next 6-9 hours, with hourly totals occasionally peaking above 0.5 in/hr. Additional rainfall through 04Z/05Z is expected to peak in the 2-4 inch range for Del Norte and Curry counties into the upslope favored terrain of the Klamath and southern Cascade Mountains below 5000-6000 feet (with snow above those levels). Considering 150-300 percent of average rainfall over the past week for the region, soil moisture and area streams/rivers are running above normal. Additional heavy rainfall may support areas of renewed flooding from northern CA into southwestern OR. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9Lz55UPUOMLTpU11Xz0IPh8_-CWEmRhcJ99NOYhx3USmhIyf7TGtxfw4lEF7rCf_6sTv= iYSbVAqlbuhDWYG2HJU5sNc$ for graphic product... ATTN...WFO...EKA...MFR...STO... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 43082448 43032431 42952407 42822382 42442370=20 42292356 42192348 42082338 42012336 41952336=20 41822339 41712340 41582333 41402328 41342325=20 41212318 41132318 41062318 40942313 40952291=20 41172255 41182246 41362207 41132197 40862226=20 40622247 40432269 40232278 40052278 39882287=20 39672293 39512301 39422323 39372358 39362393=20 39442418 39592430 40012471 40462478 41472448=20 42352476 42712481 42932472=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) .