Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Nov 04 2022 06:17:03 AWUS01 KWNH 040616 FFGMPD ORZ000-WAZ000-041530- Mesoscale Precipitation Discussion 1108 NWS Weather Prediction Center College Park MD 216 AM EDT Fri Nov 04 2022 Areas affected...Western Washington...Ext Northwest Oregon... Concerning...Heavy rainfall Valid 040630Z - 041530Z SUMMARY...Strong Atmospheric River DISCUSSION...Microwave 85/89GHz analysis and surface observations suggest the warm front is very nearly to the Western WA coast before angling away a bit just west of the northwest OR coast line. While isentropic ascent has been persistent with surface to 850mb winds out of the south, VWP at KLGX has seen a recent veering of the 925mb indicative of the warm sector starting to reach the western coastline. Higher deeper layer moisture and more importantly a deeper unidirectional flow increasing orthogonality to the terrain/coast will allow for increasing rainfall rates/efficiency. This warm sector will slowly spread over the coastal range/Olympics and eventually filter toward the western slopes of the Washington cascades bringing mid 50s Tds though the valleys and lower slopes.=20 The persistence of this warm sector will be its potency over the overnight morning hours toward late morning. The subtle variance in the pattern will be driven initially with increased moisture, followed by strengthening flow as the moisture reduces slightly with time, this should allow for consistent moderate to heavy rainfall along the mid-slopes of the terrain with steady .25"/hr rates low to .4-5"/hr rates in the mid to upper slopes of the Olympics. Mesoscale wind bursts may allow for short/occasional hours up to .7" in the mid to upper slopes of the Olympics by 12z. CIRA LPWs denote a maxima of moisture that tilts from east to west from the 500-700mb layer .3-.35" at the WA coast, .35-.45" at 700-85mb layer near 127W and .5" to .6 in the surface to 850mb layer near 130W. Winds start near the coast at 40kts at 850-700 layer before increasing to 60-70kts around 12z to 15z. So the moisture flux values will be fairly consistent with IVT values likely in the 900 kg/m/s range by early morning.=20 This should result an additional 2-3" in the lower valleys of the coastal range and lower Cascade slopes (with lowest elevations in the shadows of the Olympics across the Puget Sound to be generally less than 1". Higher portions of the west facing Olympics will see 3-5" with similar values across the mid to upper slopes of the Cascades below the freezing levels (likely to rise to 8-9Kft range). Not surprisingly, river levels will continue to rise, likely to increased rate given this expected influx of moisture, especially at higher reaches of streams/rivers. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-5UrUrT1ILuChjL8_9qGocYlj7QTaodXVnb2W5AJmpjQsJX5TwjnUn8B9FMvd4EFWMi1= 2rq6AlLguGse_uETMWosL-A$ for graphic product... ATTN...WFO...OTX...PDT...PQR...SEW... ATTN...RFC...NWRFC...NWC... LAT...LON 49042286 49012132 48602097 48092098 47212118=20 46522129 45882160 45622215 45872289 45712380=20 46252410 46992429 48142483 48362474 48182393=20 47932355 47682295 47172298 47072279 46962244=20 47192202 47612194 48042228 48492263 48812286=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) .