Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Dec 24 2022 00:49:12 FOUS30 KWBC 240049 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 748 PM EST Fri Dec 23 2022 Day 1 Valid 16Z Fri Dec 23 2022 - 12Z Sat Dec 24 2022 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley Day 2 Valid 12Z Sat Dec 24 2022 - 12Z Sun Dec 25 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE COASTAL MOUNTAINS AND CASCADES OF SOUTHERN WASHINGTON AND OREGON... ....2030Z Update... The inherited Marginal risk area has been expanded to include the southern Washington and Oregon Cascades. PWATs around 1 inch, which are 2.5 standard deviations above normal will move into the Marginal Risk area Christmas Day. High snow levels will result in all but the highest peaks getting generally 1-3 inches of rain. The rainfall combined with snowmelt should result in isolated instances of flash flooding in the Marginal Risk area. More rainfall is expected in the coastal ranges and especially the Olympics, where 2-4 inches of rain are expected, with isolated higher amounts. Thus, the Marginal Risk area is maintained. Wegman ....Previous Discussion... The arrival of an East Pacific front will advect a relatively weak plume of moisture into the Pacific Northwest on Saturday. Rain rates of around a quarter of an inch with higher values over the Olympics may support some isolated flash flooding risk. Thus, the highest qpf is likely to accumulate over the terrain, particularly the Olympic Mountains where between 2-3 inches and locally higher amounts are possible. Kebede Day 3 Valid 12Z Sun Dec 25 2022 - 12Z Mon Dec 26 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE OLYMPIC MOUNTAINS AND PENINSULA... ....2030Z Update... In contrast to Day 2, the inherited Marginal Risk area was trimmed to only include the Olympic Mountains and Peninsula, where an additional 1-3 inches of rain are expected. PWATs will remain around 1 inch for much of the day, though the greatest forcing further north will limit the atmosphere's effectiveness at wringing out that moisture as rain except in the Marginal Risk area. This rain when added to the Day 2 rainfall could cause additional isolated flash flooding. Meanwhile further south, expected rainfall amounts of around 1 inch through early Tuesday morning will not be enough to cause a significant flash flood risk. Heavy rain will redevelop in abundance further south along the CA/OR border on Tuesday. Wegman ....Previous Discussion... A new, more powerful low pressure system will enter the Gulf of Alaska on Sunday, sending a potent cold front directly into the Pacific Northwest. This cold front will be the focus for additional heavy rainfall over portions of the coastal Pacific Northwest, much like Saturday. Thus the heaviest precipitation is expected to occur over the higher elevations, especially the Olympic Mountains where the greatest chance for isolated flash flooding may occur. This marginal risk will extend south into northwestern Oregon where up to a quarter inch rates are possible. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8Bf0X-_rUnSQKNd00FariLyhmqEkKH8ts12PJsidN8BH= oAIJNd7nTc6gH9j3IwFoE1kibt7jNRqb8cRkPDDEn2cTxTI$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8Bf0X-_rUnSQKNd00FariLyhmqEkKH8ts12PJsidN8BH= oAIJNd7nTc6gH9j3IwFoE1kibt7jNRqb8cRkPDDE1umjxYc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8Bf0X-_rUnSQKNd00FariLyhmqEkKH8ts12PJsidN8BH= oAIJNd7nTc6gH9j3IwFoE1kibt7jNRqb8cRkPDDE8LEq-NA$=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) .