FOUS30 KWBC 271903 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 203 PM EST Sat Dec 27 2025 Day 1 Valid 16Z Sat Dec 27 2025 - 12Z Sun Dec 28 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Mullinax Day 2 Valid 12Z Sun Dec 28 2025 - 12Z Mon Dec 29 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR WESTERN NEW YORK... 19Z Update... The meteorological reasoning for the Marginal Risk holds today, but the focus for today's categorical risk upgrade was western NY. Flooding concerns are greatest along the Chautauqua Ridge in far western NY given not just the potential heavy rainfall rates in elevated convection, but NOHRSC shows as much as 2-4" of SWE on the ground along the Ridge. The combination of heavy rainfall, brisk southerly winds, and dew points approaching 50 degrees, is a recipe for rapid snow melt. This increases the concern for localized flooding on roads, as well as nearby creeks and streams through Sunday night. In collaboration with BUF, opted to introduce a SLight Risk over western NY where Flood Watches are present. Mullinax ---Previous Discussion--- A Marginal Risk upgrade was introduced with this morning's forecast update across a portion of the Great Lakes, in coordination with a couple of the impacted forecast offices. While the atmospheric river event in California is long over, the remnant moisture therefrom has continued east and will be harnessed by a developing storm system across the Midwest. The low center will track from near Kansas City Sunday morning to over Lake Huron by Monday morning. In that time it will deepen from around 1000 mb Sunday morning to around 974 mb Monday morning. This rapid cyclogenesis will allow the moisture to the tune of 5 sigma above normal for this time of year, as well as IVT values over 750 kg/m/s will support additional dynamic lift along the warm front which extends east of the low, and along its cold front to the low center's south. Elevated convection resulting in locally heavy rainfall is likely, despite the fast movement of any convective cells. Bare ground is in place across most of the Marginal Risk area. Due to lack of flora, it should take longer for the rainfall to penetrate into the ground, resulting in more runoff. Urban areas in the rain shield, including Chicago, Detroit, and Buffalo could see urban and small stream flooding. Across upstate New York, at the higher elevations some snowpack remains, especially east of the lower lakes. This too could locally contribute to rising stream and creek levels leading to isolated instances of flash flooding. Wegman Day 3 Valid 12Z Mon Dec 29 2025 - 12Z Tue Dec 30 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Mullinax Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt