103 FOUS30 KWBC 120048 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 848 PM EDT Sat Apr 11 2026 Day 1 Valid 01Z Sun Apr 12 2026 - 12Z Sun Apr 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN PLAINS... ...Southern Plains... Flash flooding is very much a concern from the Big Bend on north and east through the heart of TX this evening and into tonight. NAEFS shows anomalous IVT values over 500 kg/m/s (above the 97.5 climatological percentile) ahead of an approaching 200-500mb mean trough axis. Current visible satellite paints a generally broken cloud field over much of the state, although some surface based heating should allow for up to 1,000 J/kg of MLCAPE late afternoon and this evening. Storms initiating along the dryline will have a favorable vertical wind profile that sports sufficient shear (30-40kts of sfc-6km shear) and sfc-3km storm-realtive helicity (SRH) >100 m2/s2. Any discrete cells initially should manifest into a congealed cluster with some cells potentially training and back-building north of the Rio Grande. The new 12Z HREF shows pockets of moderate-to-high chances (50-80%) for rainfall totals >3" from the Rio Grande to as far north as the Red River. More concerningly, there are moderate chances (40-50%) for localized totals >5" close to Del Rio, TX. While a moderate was considered, ultimately held a Slight given the regions lower FFGs. However, this is more of a "high-end" Slight, given the potential for rainfall rates up to 2"/hr and the typical flash flood risks that the TX Hill Country has a long history of enduring. Mullinax ...Central Plains... Guidance has struggled with the renewed convection along and s-sw of the warm front across southern-central portions of KS, and although there is some convective inhibition (MUCAPES trending down over the past few hours), per the latest IR loops (streaks of cooling cloud tops), additional organized clusters will maintain the Marginal Risk area overnight into central portions of KS. Hurley ...Upper Midwest and Great Lakes... While still a non-zero threat, believe the 40km/25mi neighborhood probability of rainfall exceeding flash flood guidance is less than 5 percent. Deep-layer instability is sorely lacking, as such are rainfall rates, and even though there will be some uptick overnight (elevated CAPEs climbing between 250-500 J/Kg), the latest guidance trends, including 18Z HREF QPF exceedance probabilities, suggest that the 1-3 hourly rainfall rates will remain below FFG for the most part (i.e. likely >95% of the activity). Hurley Day 2 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. Storms will form Sunday afternoon and continue into Sunday night along and ahead of the dryline. 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... Gulf moisture will continue to transport northward and interact with the frontal boundary draped across the region. NAEFS shows PWs and IVT values that are above the 99th climatological percentile over a region that features a combination of saturated soils and lingering snowpack. An additional 1 to 2 inches of rain is forecast across the upper portion of the Mitten,causing any lingering snowpack to melt and possibly exacerbate the flooding potential on Sunday. With little change in the forecast, a Marginal Risk for Excessive Rainfall remains in effect across northern Michigan. Mullinax Day 3 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... Following a brief lull in the action Monday morning, showers and thunderstorms will return across the Upper MS Valley and into the Great Lakes Monday afternoon and into Monday night. 500mb PVA and jet streak dynamics will foster excellent vertical ascent within the column at the same time another anomalous moisture plume arrives ahead of a developing low pressure system. Additional rainfall will prolong an elevated threat for flash flooding and speed up snow melt around the region, most notably the U.P. of Michigan. A Marginal Risk remains in effect from eastern Minnesota to northern Michigan. Mullinax 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