Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Oct 29 2025 15:46:28 FOUS30 KWBC 291546 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1146 AM EDT Wed Oct 29 2025 Day 1 Valid 16Z Wed Oct 29 2025 - 12Z Thu Oct 30 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE SOUTHERN AND CENTRAL APPALACHIANS AND SURROUNDING PORTIONS OF THE OHIO/TENNESSEE VALLEYS... 16Z Update: Main change was removal of the valley areas of eastern TN where an areal min in QPF is forecast across all guidance=20 leading to limited flash flood concerns. Remainder of the forecast=20 is on track with the primary maxima still situated in the Central=20 and Southern Appalachians and neighboring Blue Ridge in VA.=20 Neighborhood probs from the latest 12z HREF were indicative of some >3" maxima situated over the Northern Neck of VA with=20 probabilities uptick to 25-50% in-of the Blue Ridge extension just=20 east of I-81. This makes sense synoptically with the increasing=20 upslope component initiating overnight into the end of the period=20 with a modest instability regime developing along the terrain and=20 points east thanks to the projected theta_E advection pattern=20 materializing as the ULL pivots eastward and we reside in=20 persistent onshore fetch from the Atlantic. Thanks to dry=20 antecedent conditions leading into the period, the setup is curbed=20 to be more in line with a MRGL risk threshold, thus maintained=20 general continuity outside the small change in TN and the western fringes of the risk area across central TN and KY. Kleebauer ...Previous Discussion.. Rainfall is expected to overspread the Tennessee/Ohio Valley with anomalous low- level moisture transport driving east-southeast moisture transport into the Southern/Central Appalachians as a closed upper low swivels from the Mid-South to the Ohio Valley. HREF neighborhood probs for >2" are relatively high in-of the Blue Ridge from Virginia down into the western Carolinas (60-90%) with a vast majority of the rain coming from shallow convective processes focused within the terrain. Large scale forcing across the aforementioned areas will be the primary driver for the heavy rain scenario, however a tongue of elevated theta_E is expected to advect off the Atlantic into the Central Apps/Blue Ridge leading to a greater potential for that low- topped convection to impact these zones. A Marginal Risk area remains in effect for this part of the nation. Campbell/Kleebauer Day 2 Valid 12Z Thu Oct 30 2025 - 12Z Fri Oct 31 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE SOUTHERN PORTION OF THE NORTHEAST... This system is forecast to track to the northeast as the associated surface low strengthens over the Mid-Atlantic onward to the Northeast. Heavy rain will accompany the low and overspread the region. The best threat for convective enhancement leading to better rates >1"/hr and some minor training off steady southeast flow off the Atlantic will occur from southeast Pennsylvania up through New Jersey, New York City metro, and western Long Island to about the I-95 corridor in Connecticut. A Marginal Risk for excessive rainfall and isolated flash flood concerns in that urbanized corridor of the Northeastern U.S. remains for this period. Campbell/Kleebauer Day 3 Valid 12Z Fri Oct 31 2025 - 12Z Sat Nov 01 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR WESTERN WASHINGTON... Heavy precipitation is likely Friday into Saturday for portions of the Pacific Northwest as a moderately strong atmospheric river streams onshore ahead of a larger northeast Pacific low. Areal averages of 1 to 3 inches will be common with the potential for local maximums of 4+ inches. A Marginal Risk for excessive rainfall and isolated flash flooding concerns is in effect for western Washington. Most precipitation is forecast to stay rain other than snow even in the highest peaks of the Olympics through Friday, with more snow in the Cascades. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7kJSuzTLBHZkElKgP-P6ZpRc5ntE2XJEFMULJCvh1_t8= AoucT_4d_f1azehg4kcMB4N51TGZcDRjZWg51pztb6JUj38$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7kJSuzTLBHZkElKgP-P6ZpRc5ntE2XJEFMULJCvh1_t8= AoucT_4d_f1azehg4kcMB4N51TGZcDRjZWg51pztknGa3UQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7kJSuzTLBHZkElKgP-P6ZpRc5ntE2XJEFMULJCvh1_t8= AoucT_4d_f1azehg4kcMB4N51TGZcDRjZWg51pztC0VkUDU$=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) .