947 FOUS30 KWBC 021955 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 355 PM EDT Thu Apr 2 2026 Day 1 Valid 16Z Thu Apr 02 2026 - 12Z Fri Apr 03 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHERN ILLINOIS, WISCONSIN AND MICHIGAN... 16Z Update: The overall setup and expected evolution remains consistent from previous forecasts with the heaviest rainfall expected to occur after 18z from eastern IA to points east and northeast as the surface low slowly intensifies and carries north- east from IA through southern WI. Warm front positioning this morning showed a modest advancement north, verifying well with the current CAMs output as the boundary begins pushing through northern IL at this hour. Expectation is for a defined warm sector to materialize across eastern IA, northern IL, and southern WI with the northern periphery of the theta_E ridge centered between the Wisconsin Dells to just south of Sheboygan. Any area south of this delineation will be under a threat of scattered convection capable of heavy rainfall with rates generally between 0.5-1"/hr with the max likely capped between 1-1.5"/hr given the instability/moisture depth present. Despite climatological anomalies of PWATs around 3 standard deviations above normal, this is still modest in the context of more appreciable rainfall prospects since it's still only the beginning of April. The primary areas of focus will be those more urbanized zones where run off potential is highest just due to the limited absorption that can occur within the infrastructure. Milwaukee, northern Chicago suburbs, and Madison are the prime targets when assessing the 12z HREF neighborhood probs for >2" as percentages are running between 40-70% from just north of the Quad Cities to the northern suburbs of Milwaukee. HREF EAS is very aggressive for at least 1" in that same broad area, however there is a precipitous drop off in the >2" EAS meaning the maximum is likely capped considering the short term training risk and then steady northeast progression as the region experiences the cold front passage later this evening. Considering the above variables, the only changes made were an adjustment further southwest with the risk into eastern IA to account for some trends in CAMs showing more aggressive convective development later this afternoon over this particular zone which upped some of the neighborhood probabilities for totals reach 2". The best chance remains across southern WI with the Milwaukee metro the most likely location for FFG exceedance and flash flood prospects. Kleebauer Day 2 Valid 12Z Fri Apr 03 2026 - 12Z Sat Apr 04 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHERN PLAINS INTO THE OZARKS AND MISSOURI VALLEY... 20Z Update: A powerful upper trough/ULL with an intensifying surface low and trailing cold front will initiate quite the heavy rain event across the Southern Plains up into the Missouri Valley on Friday evening, carrying through Saturday morning and beyond. Environment in both instability output and a deep moisture advection regime across the Southern Plains extending into the Ozarks and adjacent Missouri Valley will be prominent with PWAT anomalies surging to 2-4 standard deviations above normal within the broad warm sector centered over northern TX up into the Mid- Mississippi Valley. Large scale ascent pattern is textbook for a broad axis of maturing convection on the leading edge of the approaching cold front with the western flank of the precip situated along the cold front and a north-south oriented dryline centered over west TX. The whole setup will slowly migrate to the east as the upper level evolution gradually shifts northeastward from the Northern Plains into the Upper Midwest leading to relatively slow/modest storm motions capable of dropping copious amounts of rainfall in a short period of time. Strongest area of convergence is currently positioned where the LLJ will combine with the cold front as the boundary tilts back southwestward through TX, a classic scenario where heavy convection is more apt to train for at least a short period of time. WPC 50th percentile QPF across the area from North TX into eastern OK is between 2-3.5" the 90th percentile well over 4" for a broad area, including the DFW metroplex where flash flood concerns are always relevant due to the sprawling urbanization factors leading to high run off. 12z HREF neighborhood probabilities for >3" are between 40-80% across west-central TX to the Red River with 40-70% notable as far north as northeast OK into northwest AR. The >5" probabilities are between 20-50% across north-central TX, just north of the DFW metro and encompassing portions of I-35 and areas west. Dry antecedent conditions should prevent a more highly impactful event as initial rain will be beneficial to the region. However, the amounts being forecast in a span of 3-6 hrs as the storms move overhead would be enough to cause problems with at least a scattered flash flood prospects for where storms reach those 2-3"/hr thresholds for a time. Considering the above, this was more than enough to expand the SLGT risk further southwest into the Concho Valley and even east into the I-35 corridor within proxy of the DFW metro area. The area of eastern OK down into north- central TX is classified as a higher end SLGT risk, outside a higher risk category due to the very dry antecedent conditions initially. Will be a time frame to monitor for any targeted upgrades in these two specific areas. Further north, convective development across eastern OK up through the Ozarks and the I-49 corridor would be another area of interest, mainly late in the period, as the cold front finally reaches this area of the CONUS. Heavy rain from the previous periods over the area south of the KC metro have dropped local FFG's to values easily exceeded even in the more moderate thunderstorm outputs let alone a more significant heavy rain depiction. HREF probabilities for even >2" in the area run between 40-90% with the highest probabilities located across southwestern MO, just outside the hard hit areas referenced. Even so, the 3 and 6hr FFG exceedance probabilities in that wetter antecedent environment are well north of 60% in the latest HREF probabilities, a signature high enough to warrant an expansion of the SLGT risk further northeast out of OK and through the western Ozarks up through the I-49 corridor just southeast of Kansas City. Kleebauer Day 3 Valid 12Z Sat Apr 04 2026 - 12Z Sun Apr 05 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL AND EASTERN GREAT LAKES SOUTHWESTWARD TO CENTRAL TEXAS AND THE LOWER MISSISSIPPI RIVER VALLEY... 20Z Update: Very little has changed in the expected synoptic evolution across the eastern half of the CONUS with a broad trough and cold frontal progression likely to maintain incidences of convection stretching from the Great Lakes/Midwest down into the Mid-South and Southeastern U.S. The setup for flash flooding is still very much contingent on the convective evolution that forms upstream on D2, a tough task to engage in detail where variability in convective behavior typically causes changes in the expected QPF footprint and areal magnitudes forecast. As of now, the highest risk is likely somewhere within proximity to the Southeastern U.S., namely areas along the Lower Mississippi Valley into MS/AL as the frontal progression is expected to be within this zone around the timing of the next nocturnal LLJ enhancement. An axis of convergence between the front and LLJ will likely initiate a more robust area of heavy convection capable of flash flooding, especially in more urbanized zones. FFG's remain high overall across much of the South, so the threat for more appreciable impacts is low, but the setup could be enough to warrant a targeted upgrade. For now, the MRGL was kept due to some of the uncertainty remaining. Kleebauer ..Previous Discussion.. Much of the convection that evolves across the Marginal Risk area on D3/Sat will depend on specific evolution of convective complexes that originate from the central/southern Plains on D2/Fri. Although those details are a bit uncertain at the time frame, general consensus is that one or two MCSs will traverse the Mississippi Valley/Mid-South early in the forecast period before convective redevelopment occurs upstream along a composite outflow/cold front during peak heating hours from central Texas to Mississippi. Areas of training are likely if this pattern holds, with initiating boundaries supporting deep convection eventually becoming more parallel to steering flow aloft. Portions of this region may require an upgrade to Slight in later outlook updates. Farther north, convective coverage is far less certain - particularly from Illinois to Ohio. Deeper convection south of these areas could disrupt inflow/instability and lead to a minimum in precipitation in these areas. Again - this regime is uncertain. The primary reason Marginal was maintained for D3 from Illinois eastward to New York State and West Virginia was soils/local sensitivity. Soils are wetter with eastern extent from prior rainfall and could still be sensitive to even moderate rainfall by D3/Sat in a few spots. Cook 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