432 FOUS30 KWBC 241929 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 329 PM EDT Tue Mar 24 2026 Day 1 Valid 16Z Tue Mar 24 2026 - 12Z Wed Mar 25 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley Day 2 Valid 12Z Wed Mar 25 2026 - 12Z Thu Mar 26 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley Day 3 Valid 12Z Thu Mar 26 2026 - 12Z Fri Mar 27 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST AND OHIO VALLEY... ...1930 UTC Update... We have expanded the Marginal Risk area, notably a little farther west (into eastern IL) as well as south (into northern KY and central WV), based on the latest guidance trends (including machine learning). Always a bit tricker with these more zonal, frontogenetic setups vs. a more amplified upper trough. Strong right-entrance region forcing south of a 150+ kt northern stream jet streak will result in a quasi west-east ribbon of robust deep layer lift and moisture, with 850-700 mb moisture flux anomalies getting close to 4 standard deviations above normal as low-level trajectories originate over the western Gulf. As such, the attendant pre-frontal, west-east axes of anomalous TPWs (around 1.5") and IVTs (around 800 kg/m-s) are both 2.5 to 3 standard deviations above normal for late March. Meanwhile, current guidance (non-CAM) shows MUCAPEs averaging 1,000 J/Kg Thursday night along and ahead (south) of the front, which along with with robust deep layer shear (0-6km bulk shear 50-70 kts), would be plenty supportive of widespread, organized convection along and ahead of the front. Given this degree of dynamic and thermodynamic support, along with the low-level flow in near alignment with the mean 850-300 mb flow, believe short term rainfall rates will be quite prolific for a while before the the front pushes south -- likely to the tune of 1 to 1.5+" within an hour within the strongest cores. After talking with the OHRFC, we toyed with the idea of including a targeted Slight Risk within the now broader Marginal Risk area, however we opted no to for now given the spread in the model QPFs. Expect to get more clarity on this as the event gets into the high-res CAM windows. Hurley ...Previous Discussion... A strong cold front will move southward across the Midwest Thursday night. The front will run into a marginally unstable and warm air mass, but with limited moisture with surface dew points on either side of 60 degrees. Nonetheless, with some upper level support and significant shear, organized thunderstorms are likely to form Thursday evening. The storms could then train over many of the same areas that saw some heavy rain from a very similar-behaving front yesterday. This is a lower-end Marginal Risk as upper level support and instability will both not be quite as favorable to the storms as yesterday. This will be somewhat offset by a bit wetter soils by then than they were before yesterday's rainfall event. The areas most likely to see an instance or two of flash flooding are the urban centers. Should forecast rainfall decrease, which appears possible, the Marginal may be able to be dropped with future updates. Wegman 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