295 FOUS30 KWBC 111915 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 315 PM EDT Sat Apr 11 2026 Day 1 Valid 16Z Sat Apr 11 2026 - 12Z Sun Apr 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN PLAINS... ...Central Plains... The MCS responsible for periods of excessive rainfall and resulting flash flooding will continue through the remainder of this morning. The 12Z TOP sounding shows as much as 1,000 J/kg of MUCAPE, along with a saturated and nearly 8,000ft warm cloud layer aloft, plus a highly sheared environment featuring excellent low- level SRH in the sfc-1km layer that exceeds 250 m2/s2. The ARW has handled this complex the best, and its new 12Z run suggests organized thunderstorms will linger for at least a couple more hours over northeast KS and far northwest MO. WPC has issued a new MPD, #0091, to highlight the ongoing flash flood threat. But with several more hours of excessive rainfall expected, opted to maintain the Marginal Risk until at least the 01Z update. Mullinax ...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 ---Previous Discussion--- The presence of an increasing southerly low level will transport Gulf moisture northward and pool over the Plains and Mississippi Valley as an upper level trough enters the West and ridging builds over the East. Meanwhile the upper dynamics and embedded shortwave energy will support ascent ahead of a longwave trough. At the surface, a dry line across West Texas will help serve as an initiating mechanism for convection in the afternoon. Strong to severe thunderstorms are expected to fire up over the Southern and Central High Plains, migrating eastward eventually making headway into the adjacent Concho Valley and lower Trans Pecos. As cells merge due to cold pool mergers and low-level jet initiation, a large cluster of heavy rainfall will ensue through the rest of Saturday night into Sunday morning. General consensus maintains 2-4 inches possible from the Concho Valley in West Texas to the Red River Valley in southern Oklahoma. Neighborhood 24 hr QPF HREF probabilities show a strong signal for 50-80% for 2 inches for this region and 40-70% for 3 inches. A Slight Risk for Excessive Rainfall remains in effect across portions of the Southern Plains, especially the areas referenced above. Campbell ...Upper Midwest and Great Lakes... The Marginal Risk was expanded southward into southern WI, northeast IA, and northern IL for the 16Z update. Latest ARW and HRRR have trended south with their QPF axis with storms forming closer to the lifting warming front. This setup has eerily similar characteristics that led to the flash flooding in northeast KS this morning; sheared lobes of 500mb vorticity to the west of the upper-level ridge axis with area-averaged soundings showing notable low-level SRH values and over 500 J/kg of MUCAPE aloft. Warm cloud layers at least 8,000ft deep and NAEFS highlighting a robust 750 kg/m/s IVT over central IA being aimed at southern WI tonight also supported both warm rain processes and healthy moisture advection. 1-hr FFGs remain as low as 1" in some locations given the saturated soils in place. With these factors accounted for, the Marginal Risk will focus on the potential for flash flooding in these aforementioned areas tonight and into the early morning hours on Sunday. Mullinax ---Previous Discussion--- Scattered to widespread convection is expected across parts of Wisconsin and Michigan as moisture increase along a warm front lifting northward through the region. Areal averages of around 1 inch are still on track. Much of the region will be sensitive to additional precipitation as there has been ongoing snow melt and high river flows. Although it may be isolated, flash flooding may be possible during this period. A Flood Watch remains in effect across the Michigan U.P. and far northern Lower Michigan and Wisconsin. Campbell 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