Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Nov 05 2022 00:05:43 AWUS01 KWNH 050005 FFGMPD ORZ000-WAZ000-050803- Mesoscale Precipitation Discussion 1111 NWS Weather Prediction Center College Park MD 804 PM EDT Fri Nov 04 2022 Areas affected...Western WA and Northwest OR Concerning...Heavy rainfall...Flash flooding possible Valid 050003Z - 050803Z SUMMARY...Strong atmospheric river conditions will continue into the overnight hours, but will settle farther south and increase the impacts across northwest OR. The longevity of the heavy rainfall will maintain concerns for runoff problems and urban flooding, with some flash flooding and debris flow activity still possible for the local burn scar areas in the Cascades. DISCUSSION...Compared to earlier in the day, the overall orientation of the strong atmospheric river impacting the Pacific Northwest has shifted a bit down to the southeast, and this is allowing for the core of strongest moisture transport and heaviest rainfall to shift down across the coastal ranges of southwest WA, northwest OR and the adjacent areas of the Cascade Range off to the east. GOES-17 satellite imagery shows a strong upper trough over the Gulf of Alaska making progress in dropping down to the southeast which is driving a cold front down across Vancouver Island and this front will begin crossing the Olympic Peninsula by later this evening, and the interior of the Pacific Northwest later tonight. The moisture transport ahead of this cold front though remains quite strong and with proximity of a west-southwest low-level of 50 to 60+ kts and thus still largely orthogonal to the coastal ranges and the Cascades. IVT magnitudes are forecast to peak this evening a bit over 1000 kg/m/s across southwest WA and northwest OR, with values a bit lower and closer to 750 kg/m/s farther inland over the Cascades. The heaviest rains should coincide with this channel of enhanced IVT, and coupled with the orographics, should continue to support rainfall rates that reach 0.5" to 0.75"/hour with isolated rates possibly reaching hitting the 0.75" to 1"/hour range. Already over the last 24 hours, there has been widespread 3 to 6 inch rainfall totals over the coastal ranges from the Olympic Peninsula southward into far northwest OR, and across the windward slopes of the Cascades off to the east. A few spotty 6 to 8 inch totals are have been reported as well. Additional rainfall amounts of 2 to 4+ inches will be possible over the higher terrain (lesser amounts of 1 to 2+ inches for the interior valleys) going through midnight local time. However, the the focus of heavy rainfall will continue to gradually settle farther south and deeper down across western and northern OR as the aforementioned cold front and supporting upper trough arrives from the northwest. Farther north as the cold front crosses western WA, the steady rains should come to an end with more of showery post-frontal regime thereafter. The additional rains this evening and overnight though will maintain the threat of runoff problems and urban flooding, and given the rather high rainfall rates, there will also still be a concern for flash flooding and debris flow activity around the local burn scar areas in the Cascades. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5jUxqChp6DzRP_iF5N7e4dr69u2K5qQ8xybw49hsoLUBmM_jIL4D3LxIFjw8I2puq4_2= nMmJUBbivXfqvmKq-1Tz5fQ$ for graphic product... ATTN...WFO...MFR...OTX...PDT...PQR...SEW... ATTN...RFC...NWRFC...NWC... LAT...LON 48822199 48762145 48432120 47782104 47162103=20 46282117 45712128 44392157 43572188 43372246=20 43612316 43462401 43762443 45512407 46972434=20 47772464 48022478 48252465 48172401 47802330=20 47102291 47052247 47342208 48372219=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) .