Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Oct 30 2025 07:20:33 FOUS30 KWBC 300720 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 320 AM EDT Thu Oct 30 2025 Day 1 Valid 12Z Thu Oct 30 2025 - 12Z Fri Oct 31 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID ATLANTIC AND NORTHEAST... An occluded cyclone is forecast to track to the northeast as its=20 surface low strengthens over the Mid-Atlantic and moves northeast, drawing in increasingly higher moisture from Hurricane Melissa.=20 Strong 850 hPa inflow near 50 kts and sufficient instability (500+=20 J/kg of MU CAPE) is forecast to overspread the region. Hourly=20 amounts rising into the 1-2" range could occur from southeast=20 Pennsylvania up through New Jersey, Long Island, and portions of=20 southwest New England, with local totals to 4" possible within 2-3 hours. Despite recent drought, this could be problematic in urban=20 areas and where recent leaf fall has clogged drainage.=20 A Marginal Risk for excessive rainfall and isolated flash flood=20 concerns remains for this period; the system's progression should=20 hold off any broad areas with a higher risk of flash flooding. It=20 should be noted, however, that a spot or two within southern=20 Upstate NY and northeast PA have a ~20% chance of 5"+ per the HREF and REFS guidance, so localized Slight Risk impacts cannot be=20 ruled out. Roth Day 2 Valid 12Z Fri Oct 31 2025 - 12Z Sat Nov 01 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR NORTHWESTERN WASHINGTON STATE... A modestly strong atmospheric river will setup across the Pacific Northwest Northwest with an advection of high IVT (>750 Kg/ms)=20 into the region beginning Friday afternoon, carrying through the=20 late evening Friday into Saturday. Inflow at 850 hPa approaches 50 kts out of the southwest while precipitable water values in the=20 coastal ranges rise into the 1.25-1.5" range. MU CAPE is forecast to remain weak, under 250 J/kg. Precip rates should rise to=20 between 0.5-0.75"/hr during the peak of the heavy rainfall,=20 producing local amounts of 3-5" in the higher terrain of western=20 WA, which would be particularly challenging for the Skokomish=20 river. Considering the consistency within guidance on totals and=20 expectation for some enhanced rates to generate river rises and=20 minor flooding, a Marginal Risk was maintained, with some expansion to the south to account for the wetter 00z UKMET solution. Roth Day 3 Valid 12Z Sat Nov 01 2025 - 12Z Sun Nov 02 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Roth Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5Ex90g5M7BJ3KPIMmdKw4AxrcwEGhyE5RdPJVzi9QAIS= wLhbY2fOhSjtDkqe16YaEqjwk39tuiYCMeCY7eYu4opIqnM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5Ex90g5M7BJ3KPIMmdKw4AxrcwEGhyE5RdPJVzi9QAIS= wLhbY2fOhSjtDkqe16YaEqjwk39tuiYCMeCY7eYuqSgtVGQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5Ex90g5M7BJ3KPIMmdKw4AxrcwEGhyE5RdPJVzi9QAIS= wLhbY2fOhSjtDkqe16YaEqjwk39tuiYCMeCY7eYuBMmmPlw$=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) .