Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
803 FOUS30 KWBC 251925 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 225 PM EST Tue Nov 25 2025 Day 1 Valid 16Z Tue Nov 25 2025 - 12Z Wed Nov 26 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHEAST AND SOUTHERN APPALACHIANS, SOUTH TEXAS, AND ALSO FOR THE COASTAL PACIFIC NORTHWEST... ...16Z Outlook Update... The ongoing forecast is generally on track with only minimal changes needed based on latest short-term convective evolution. Reference Mesoscale Precipitation Discussion #1250 for short-term flash flood risk evolution across Alabama and vicinity. Later today, convection will increase in coverage and intensity across eastern Mississippi and migrate quickly eastward across Alabama into Georgia and southeastern Tennessee through the overnight hours. CAMs depict a mix of cellular and linear convective models with little opportunity for convective training that would enhance local flash flood risk. Marginal Risk and attendant probabilities remain appropriate for today`s flash flood threat, with urban areas, sensitive/low-lying areas, and areas that have wet soils from prior rainfall (i.e., western/northern Alabama) experiencing a locally higher (but still isolated) threat of excessive runoff. A small Marginal Risk area was drawn for Deep South Texas primarily for the overnight (03Z-12Z) period. A stalling front should drift toward that area during that timeframe. Meanwhile, weak mid-level waves should initiate convection along and south of the front where moderate instability and very moist thermodynamics reside (PW values ~ 1.75 inch). While sufficient steering flow aloft exist for appreciable cell movement, any localized backbuilding near the front could prompt local 3 inch rainfall amounts that could cause excessive runoff especially near urban/sensitive locales. The remainder of the forecast (with Marginal Risk/probabilities for excessive runoff across the Pacific Northwest) is on track. See the prior forecast below for more information. Cook ...Previous Discussion... ...Southeast states... The storm system crossing the southern tier states will continue to have a plume of Gulf moisture surging north ahead of the cold front through Tuesday afternoon, mainly from southeastern Mississippi to the southern Appalachians. The magnitude of the rainfall and also the coverage is expected to wane compared to yesterday as the storm system becomes more elongated and progressive. Recent CAM guidance has swaths of QPF maxima on the order of 1.5 to 3 inches from central Alabama to eastern Tennessee and western North Carolina, with the RRFS taking some of the heavier rains as far north as the Kentucky state line. Only small changes were necessary to the inherited Marginal Risk area, with a modest extension northward to include more of the southern Appalachians, and a little farther westward to areas closer to the Mississippi border. ...Pacific Northwest... A marginal atmospheric river event will affect the coastal ranges and the Cascades from central Oregon northward through Tuesday night, followed by lighter precipitation going into Wednesday. There will not be much instability to work with, so this will tend to keep rainfall rates in check, but the duration of moderate rainfall with rates near 0.25 inches per hour leading to areas of 1-2 inch daily rainfall totals may just be enough to lead to some localized instances of minor flooding from the northern coastal ranges of Oregon to the Olympic Peninsula. The timing for this has also sped up some, to the point where the majority of the rainfall is now expected in the Day 1 period instead of the Day 2 period, so no areas are necessary at this time beyond 12Z Wednesday for this region. Hamrick Day 2 Valid 12Z Wed Nov 26 2025 - 12Z Thu Nov 27 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 3 Valid 12Z Thu Nov 27 2025 - 12Z Fri Nov 28 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard 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