Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Dec 10 2023 02:13:19 AWUS01 KWNH 100213 FFGMPD ORZ000-WAZ000-101410- Mesoscale Precipitation Discussion 1192 NWS Weather Prediction Center College Park MD 911 PM EST Sat Dec 09 2023 Areas affected...Portions of the Pacific Northwest Concerning...Heavy rainfall Valid 100210Z - 101410Z SUMMARY...Ongoing moderately strong atmospheric river activity will continue to bring heavy rainfall inland overnight across portions of the Pacific Northwest. DISCUSSION...The latest GOES-W IR/WV suite shows a well-defined atmospheric river once again impacting the Pacific Northwest. IVT values are currently peaking on the order of 500 to 750 kg/m/s across the coastal ranges of southwest WA and into northwest OR as a cold front offshore continues to gradually approach the region. Facilitating these stronger IVT values is the presence of a 50+ kt west-southwest low-level jet which is helping to drive 850/700mb moisture flux anomalies that are a solid 2 to 3 standard deviations above normal. Rainfall rates over the last several hours have been peaking generally within the 0.20" to 0.30"/hour range and have been aided rather strongly by the overall orthgonal orientation of the moisture transport regime into the higher terrain of the coastal ranges and the upslope areas of the Cascades. As the offshore Pacific cold front advances inland, the latest HRRR guidance along with the 18Z HREF member suite suggests the strongest axis of IVT values will gradually settle south overnight and generally impact the central and northwest OR coastal ranges and into the northern OR and southern WA Cascades with the heaviest rainfall rates. Some further uptick in rainfall rates that may reach or briefly exceed a 0.50"/hour can be expected for these locations, and additional rainfall totals going through 12Z are expected to reach 3 to 4 inches with isolated heavier amounts not out of the question for areas of far southwest WA/northwest OR and into the favored upslope areas of the southern WA/northern OR Cascades, and this will also be aligned with the axis of strongest IVT and orographic forcing. Given the very wet antecedent conditions, the additional rainfall amounts will support a threat for some runoff problems.; Conditions should gradually begin to improve after 12Z as the overall atmospheric river itself weakens and the rainfall rates begin to gradually subside. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!--2LEZUx7NGgacgNeEiejr1nVA5ZWyx4wakC2vEEncBedBgx72bNTqlljQBiSn-53eus= ET2NMi8eGNVlUdI9hwlXA0M$ for graphic product... ATTN...WFO...PDT...PQR...SEW... ATTN...RFC...NWRFC...NWC... LAT...LON 47762353 47052311 46662307 46372293 46282252=20 46342196 46182162 45682141 44802167 44442219=20 44572267 45062272 45002320 44562341 44472418=20 44842443 46052411 46992427 47662454=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) .