Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Oct 31 2025 19:45:05 FOUS30 KWBC 311944 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 344 PM EDT Fri Oct 31 2025 Day 1 Valid 16Z Fri Oct 31 2025 - 12Z Sat Nov 01 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN WASHINGTON AND FAR NORTHWESTERN OREGON... ....16Z Outlook Update... The ongoing forecast is on track, with only minimal spatial extensions to the Marginal Risk area to account for areas of greatest heavy rain likelihood tonight through 12Z Sat. See the previous discussion below for additional details. Cook ....Previous Discussion... A modestly strong atmospheric river will setup across the Pacific Northwest with an advection of high IVT (>750 Kg/ms) into the region from afternoon through late evening. Inflow at 850 hPa approaches 50 kts out of the southwest while precipitable water values in the coastal ranges rise into the 1.25-1.5" range, though little to no instability is forecast. Precip rates will generally remain below 0.5"/hr, but may locally peak between 0.5-0.75"/hr. This may result in localized amounts of 2-5" in the higher terrain of western WA and far northwestern OR, which would be particularly challenging for the Skokomish river. Given the consistency of the forecast and the expectation for some enhanced rates to generate river rises and minor flooding, a Marginal Risk was maintained and expanded a bit south into far northwestern OR. Churchill/Roth Day 2 Valid 12Z Sat Nov 01 2025 - 12Z Sun Nov 02 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN WASHINGTON AND FAR NORTHWESTERN OREGON... ....21Z Outlook Update... The Marginal Risk area in effect for Day1/Fri has been extended into this forecast period. A landfalling atmospheric river will continue to spread moderate to occasionally heavy rainfall across much of western Washington and northwestern Oregon through at least the 18Z Sat through 00Z Sun timeframe. Any ongoing flood/flash flood issues could continue, with problems most likely near full watersheds (inhibiting runoff), burn scars, and other locally sensitive areas. An additional 1-2 inch rainfall totals (with locally higher amounts) are expected. Cook Day 3 Valid 12Z Sun Nov 02 2025 - 12Z Mon Nov 03 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Cook/Churchill Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8Wb2D5stidVsmcJRFKPy-nIH117Pi_x0t2-v5IjdEmua= Zaw2SKBhrJ3og9rkWEjM1TxC_5DIoUR8wh4oKrKaV-VgueQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8Wb2D5stidVsmcJRFKPy-nIH117Pi_x0t2-v5IjdEmua= Zaw2SKBhrJ3og9rkWEjM1TxC_5DIoUR8wh4oKrKaRDirktE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8Wb2D5stidVsmcJRFKPy-nIH117Pi_x0t2-v5IjdEmua= Zaw2SKBhrJ3og9rkWEjM1TxC_5DIoUR8wh4oKrKa8TgtwI0$=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: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .