FOUS30 KWBC 150051 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 851 PM EDT Tue Apr 14 2026 Day 1 Valid 01Z Wed Apr 15 2026 - 12Z Wed Apr 15 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF THE UPPER MIDWEST TO THE OHIO VALLEY... ... Ohio Valley... Only minor adjustments were made based on short-term radar imagery but did not reflect whole-sale change in previous forecast reasoning. The latest HREF and ARW runs still favored the area while rainfall and related probability of exceedance from the RRFS were lower. High seasonable PWATS and abundant instability also support the potential for high hourly rainfall rates. ...Wisconsin and Michigan... Made a northward expansion of the Slight risk in parts of Wisconsin and Michigan in response to short-term trends in radar and satellite imagery. Given the placement of convecitive initiation...starting to give more credence to the HREF camp for overnight convection and risk of excessive rainfall. In particular, concern involves the potential for storms to expand northeastward and eastward across Wisconsin and northeast Iowa given favorable interaction if a warm front at the surface and steep mid-level lapse rates yielding 1.5 to 2 inch per hour rates in the shorter term before rates begin to diminish...although areas downstream have been made more prone to flooding by 3 to 5 inch rainfall amounts over the past few days. See MPD 0105 for further details. ...Iowa/Illinois... Expanded the Slight Risk area westward into Iowa in the wake of one round of showers and thundersotms over the northeast part of the state due to concern over convective redevelopment. Normally this would be a candidate for removal from the Slight risk area...but moist south to southwest flow at low levels over-running the surface outflow boundary has the potential to ignite addition storms capable of producing locally intense rainfall rates. If that scenario is realized...rainfall rates in excess of 1 inch per hour are possible where 1-hour Flash Flood Guidance is comparable...with the potential for storms to track along that same interface into Illinois. See MPD 0106 for further details. ...Central Plains southwestward to the Lower Trans-Pecos/Big Bend... ...Oklahoma and Kansas... A broad corridor of moisture and instability is expected to remain in place overnight...with the HREF and RRFS indicating the potential for multiple rounds of convectionn firing in proximity to the dryline. HREF neighborhood probabilties of 24 hour rainfall exceeding 2 inches are fairly high (50-70%) and 20-40% for exceeding 3 inches. With a steady stream of PW values of 1.25 to 1.5 inches being advecting northward through the Southern/Central Plains nearly parallel to the dryline...slow storm motion is expected, Much as before...this Marginal Risk area was a southwestward extension of the excessive rainfall outlook areas over parts of the Upper Midwest/Great Lakes region. Bann Day 2 Valid 12Z Wed Apr 15 2026 - 12Z Thu Apr 16 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR THE GREAT LAKES AND NORTHERN OHIO VALLEY.. The surface to mid-level environment remains very similar to the past couple of days with a stark dry line extending from the Pecos River Valley across the Southern Plains into the Upper Mississippi Valley. A stationary front will continue to align west to east from Illinois to New York and serve as a mechanism for heavy rainfall potential. The longwave trough will finally be making progress toward the Central Plains and the deep layer moisture axis and instability shifts slightly eastward. An upgrade to a Slight Risk for Excessive Rainfall was added across southern Wisconsin and Michigan. Across the northern Ohio Valley, northern Illinois, Indiana, and Ohio were included in the risk area. A persistence forecast worked well here where instability, plentiful moisture near the surface (PWATS near or exceeding 1.5 inches), and a nearby stationary boundary and weak area of low pressure will help create an environment capable of producing heavy rainfall. WPC QPF indicates 1-3 inches of rain over the same regions that have have seen rounds of heavy rainfall over the past couple of days. The flash flood guidance, meanwhile, has lowered to a half an inch to an inch. Another consideration was the flash flood sensitivity for urban areas such as Milwaukee, Chicago, and Detroit. The Slight Risk does extend southward across northern Illinois and Indiana to account for uncertainty on storm track and the spread of 2 inch HREF 24 hr QPF neighborhood probability. ...Eastern Oklahoma and the Ozarks... Similar to the past couple of days, afternoon storms are likely to form and trek from the southwest to northeast ahead of the longwave trough moving into the Central Plains. Eastern Oklahoma into the Ozarks will be in the right entrance of the jet streak, which will help provide lift. At the surface, high PWATS and surface instability will once again prime the atmosphere for hourly rainfall rates of an inch/hr. QPF guidance does show a maximum of 1-2 inches across the region, but model guidance shows little to no probability for accumulations exceeding 2 inches. Therefore, a Marginal Risk is maintained for the risk area. Additionally, the more flash flood prone Ozark mountain range is relatively dry. ...Northeast... A Marginal Risk for Excessive Rainfall was expanded eastward across New York State to Connecticut. Moisture transport will increase across the east as the longwave trough shifts eastward into the center of the country. Additionally, weak areas of low pressure will ride along a stationary boundary across the Northeast that will help funnel moisture across the area. Remnants of the storms across the Great Lakes may bring a round of showers and storms in the morning, followed by another round of heavier showers and thunderstorms in the afternoon. Model guidance shows a corridor of 1-1.5 inches rainfall with embedded higher amounts depending on the model. The relatively lower flash guidance across western Pennsylvania and the more urban footprint of areas such as Connecticut and New England also help confidence of expanding the Marginal eastward. Wilder Day 3 Valid 12Z Thu Apr 16 2026 - 12Z Fri Apr 17 2026 The probability of rainfall exceeding flash flooding guidance is less than 5 percent. Wilder 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