BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Thu, 19 Mar 2026 18:35:26 +0000 ----------------------------------------------------------- FOUS30 KWBC 191835 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 235 PM EDT Thu Mar 19 2026 Day 1 Valid 16Z Thu Mar 19 2026 - 12Z Fri Mar 20 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF WESTERN WASHINGTON STATE... ...16Z update... No changes were made for this update with another day of steady, locally heavy, rainfall expected for western Washington. The 12Z HREF guidance did not show significant changes from the 00Z cycle and an additional 2-4 inches of rain through Friday morning still looks reasonable within the favored southwest facing slopes of the Olympics into the Cascades (locally higher possible). Hourly rainfall is likely to remain below 0.5 inches and of concern for flash flooding, but an isolated threat will still exist, with elevated rivers/streams and soil moisture a concern given antecedent rainfall over the past several days. Otto ...previous discussion follows... An atmospheric river of moisture and rainfall originating from the tropics near Hawaii (a.k.a. Pineapple Express) will be directed at the Olympics and Cascades of western Washington State on Thursday. The plume will be guided by a large and very anomalously strong upper level high/ridge over the Southwest, and a series of lows, both over the Pacific and the Gulf of Alaska. The plume itself will be anomalous in that the moisture content will be between 3 and 4 sigma above normal for March for western Washington as PWATs exceed an inch. Heavy rain will impact much of western Washington through the day on Thursday. A brief diminishing of the rain is expected through the first half of Thursday night before a weak wave of low pressure moves into southern British Columbia, and another round of heavier rain moves in after midnight. Total rainfall amounts will be in the 2-4 inch range in the Olympics and northern Cascades. This rain will be on top of already saturated soils from prior rain events, so much of the new rainfall will quickly convert to runoff. Isolated flash flooding is probable, especially in urban and flood-prone areas. Wegman Day 2 Valid 12Z Fri Mar 20 2026 - 12Z Sat Mar 21 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF WESTERN WASHINGTON STATE... 19Z Update... No changes were made to the previous forecast. The 12Z HREF continues to support an additional 1-2 inches in the Olympics and the 2-3 inches along the western slopes of the northern Washington Cascades. Pereira Previous discussion... A weak wave of low pressure will move ashore into Vancouver Island very early Friday morning. The moisture associated with its trailing front will continue the heavy rain into western Washington from overnight Thursday night. The low will dissipate in southern British Columbia during the day Thursday, but the associated rainfall will likely continue for much of the day Friday. Once the center of the low reforms over the Plains in Alberta, the flow will weaken enough to end any upslope into western Washington, and ending the rainfall event. Nevertheless, expect an additional 1-2 inches of rain into the Olympics and another 2-3 inches into the Washington Cascades before the rain ends. Given plentiful earlier rains from Day 1/Thursday, there is some potential for flooding to be ongoing at the start of the period. In which case, additional rainfall could worsen ongoing flooding and/or initiate new flooding. A Slight Risk upgrade could be needed with future updates in the northern Cascades. Wegman Day 3 Valid 12Z Sat Mar 21 2026 - 12Z Sun Mar 22 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_9e__NYJEywnJlO21lGtMdu2KgzNEK7GqUma6dOqtU9B= afHMXZZjcxiVZAL9HAzvfvQRt6BIFAYxf6D5ohQLwoNGTgE$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_9e__NYJEywnJlO21lGtMdu2KgzNEK7GqUma6dOqtU9B= afHMXZZjcxiVZAL9HAzvfvQRt6BIFAYxf6D5ohQLuzYaipA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_9e__NYJEywnJlO21lGtMdu2KgzNEK7GqUma6dOqtU9B= afHMXZZjcxiVZAL9HAzvfvQRt6BIFAYxf6D5ohQLjxalIpY$=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 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]