FOUS30 KWBC 120810 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 410 AM EDT Sun Apr 12 2026 Day 1 Valid 12Z Sun Apr 12 2026 - 12Z Mon Apr 13 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR CENTRAL TEXAS... ...Central Texas... Broad troughing in the west will continue to direct sheared 500mb vorticity maxima at the Southern Plains as a narrow 250mb jet streak over the Central Plains places its divergent right-entrance region over central and southern TX. Between the trough in the West and high pressure over the Southeast, a strong IVT exceeding 500 kg/m/s will engulf much of the Southern Plains with 1,000-2,000 J/kg of MLCAPE. Convection will fire up along and ahead of the dryline during the afternoon and evening hours. Vertical wind shear and low-level helicity will be sufficient to support strong- to- severe storms, but the uncertainty lies in the orientation of surface troughs and outflow boundaries that reinvigorate storms Sunday night, and where they are located. Some CAMs show some more progressive segments of storms, while others show potential for back-building and training. 12Z HREF guidance, specifically 24-hr QPF probabilities, show moderate chances (40-60%) for rainfall totals >2", with the bulk of the rainfall coming after 18Z and before 12Z Sunday. There are some low chance probabilities (20-30%) along I-35 from San Antonio to Austin. Southern and eastern TX badly need rainfall (UNL drought monitor shows severe drought in many places), but excessive rainfall rates approaching 2"/hr over very dry/hard ground can become hydrophobic. Add in the metro areas at risk (I-35 corridor) and the inherited Slight Risk still looks to be on track. The expansive area of anomalous moisture (>90th climatological percentile per NAEFS) extends as far north as eastern OK, southeast KS, and southwest MO. Excessive Rainfall in these areas will be largely driven by the aforementioned 250mb jet streak as southerly 850mb winds inject the moisture into this divergent setup aloft. Soundings are not as saturated and storm motions are faster, thus supporting the Marginal Risk currently in place. ...Northern Michigan... A Marginal Risk remains in effect for this period. Anomalous Gulf moisture pumping northward will interact with the draped frontal boundary to bring enhanced rainfall to the region. NAEFS continue to show PWs and IVT values that are above the 99th climatological percentile that features a combination of saturated soils and lingering snowpack. Accumulations of 1 to 2 inches are anticipated for the northern half of Mitten which may cause any lingering snowpack to melt and possibly exacerbate the flooding potential on Sunday. Campbell/Mullinax Day 2 Valid 12Z Mon Apr 13 2026 - 12Z Tue Apr 14 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE UPPER MISSISSIPPI VALLEY AND UPPER GREAT LAKES REGION... Another round of showers and thunderstorms will move through the Upper Mississippi Valley and Great Lakes during the afternoon and evening hours, prolonging the threat for excessive rainfall, increased snow melt and flash flooding. A Marginal Risk remains in effect from eastern Minnesota to northern Michigan. Campbell Day 3 Valid 12Z Tue Apr 14 2026 - 12Z Wed Apr 15 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE TEXAS HILL COUNTRY TO THE UPPER MIDWEST/GREAT LAKES REGION... Multiple rounds of strong to severe thunderstorms expected from Texas to the Midwest states, given favorable wind shear and instability in place as multiple impulses eject across the Plains. Gulf moisture will be funneling northward between the trough over the Rockies and the ridge over the eastern states. The environment will be favorable for a few mesoscale convective systems to develop and the limited eastward progression will likely result in areas that have excessive rainfall leading to some instances of flash flooding. A Marginal Risk area span from the Texas Hill Country northeastward to the Midwest and western Great Lakes. Campbell 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