FOUS30 KWBC 071949 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 349 PM EDT Sun Jun 7 2026 Day 1 Valid 1934Z Sun Jun 07 2026 - 12Z Mon Jun 08 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR NORTHERN ALABAMA... Special 20Z Update... Ongoing heavy rain in northern AL, where radar estimates have exceeded 4-6" by 19Z, has led to several reports of flash flooding. This activity is forecast to continue through this evening along an axis of convergence in northern AL that may gradually slide southward until instability wanes following sunset and overall thunderstorm activity diminishes. However, an additional 1-3" of rain is possible and any rain is likely to compound ongoing widespread flooding impacts with some significant flooding possible. See MPD 0351 for more information. 16Z Update... Forecast remains on track for widely scattered to numerous clusters of thunderstorms to impact a vast region of the central U.S. from the northern Plains to the Tennessee Valley and central Gulf Coast. These thunderstorms may be slow-moving at times and contain very intense rainfall rates within a highly buoyant and moisture-rich atmosphere. Changes to the outlook include removing some of northeast ND and northern MN from the Marginal Risk as well as expanding the Slight Risk across central IN given latest 12Z model trends. One area of interest that will be monitored through tomorrow (Monday) morning is near the Ozarks into eastern OK and southeast KS, where a backbuilding cluster of the thunderstorms now seems likely to develop late- tonight into early Monday morning. This will be associated with a lifting MCV out of northern Texas today and interact with the strengthening LLJ overnight to create an overrunning scenario within an unstable and highly moist atmosphere. Still some uncertainty with the location of this event and will likely extend beyond the "Day 1" forecast period valid through 12Z Monday. 12Z HREF and REFS probabilities for at least 5" of rainfall within 12-hrs ending 12Z Monday are between 20-40%. Several CAMs suggest 7-10" rainfall totals are possible should the "worst case scenario occur" with this nocturnal complex of thunderstorms developing and maintaining itself. If guidance comes into better agreement before this evening regarding the location of this narrow band of heavy rain, an upgrade to a Moderate Risk is possible. Snell Previous Discussion... Numerous thunderstorms are expected to form this afternoon into tonight over a broad area spanning across the Great Plains and Mississippi, Ohio, and Tennessee Valleys. Three primary forcings will trigger storms: an upper level shortwave moving north across the central Plains, Mid-Mississippi Valley, and Upper Midwest, a strengthening cyclone emerging in the northern/central Plains, and a quasi-stationary frontal boundary draped across the Mid- Mississippi and Ohio Valleys. These features will interact with a moist, unstable air mass that will support efficient rainfall processes that could lead to heavy rainfall. Deep, moist southerly flow has primed the atmosphere across the Plains and Mississippi Valley, increasing PWAT values to around 2 inches (2-2.5 standard deviations above normal for this time of year). Hi-res CAM guidance suggests rainfall rates of 2-4 inches per hour will be possible in thunderstorm cells across the Mid-Mississippi Valley and portions of the Ozarks and western Tennessee Valley, which would exceed current flash flood guidance and result in scattered instances of flash flooding within the Slight Risk area. Areas from eastern Oklahoma into western Arkansas and east-central Illinois into west- central Indiana may be more susceptible to flash flooding after rainfall yesterday left soils thoroughly saturated. Heavy rain will likely result in locally high rainfall totals, potentially reaching 5-7 inches for some locations within the Slight Risk area. Locally heavy rainfall will also extend along the quasi-stationary frontal boundary into Ohio Valley. Storms forming along the boundary will have the potential to produce rainfall rates over 2 inches per hour, and storm motion will be fairly slow. However, convection should be more isolated over the Ohio Valley portion of the front, resulting in only a Marginal Risk. Stronger convection will also be possible in the vicinity of the low pressure system over the northern Plains, but storms will be much more progressive in this region, which will limit heavy rainfall potential and the risk of flash flooding. The Marginal Risk area extends across the northern Plains to account for isolated flash flood potential with stronger thunderstorms that may form. Dolan Day 2 Valid 12Z Mon Jun 08 2026 - 12Z Tue Jun 09 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MID-MISSISSIPPI, LOWER OHIO, AND TENNESSEE VALLEYS... On Monday, the northern stream cyclone will move north into Canada, while the leading shortwave trough and embedded MCV activity pushes east across the Midwest and Tennessee Valley. At the same time, a cold front sinking southward along the Carolinas will drape as a stationary front into the Ohio Valley and Midwest. Heavy rainfall potential will be focused in the warm sector of the system over the Mid- Mississippi, lower Ohio, and Tennessee Valleys where a very moist and unstable air mass will still be in place. The splitting upper level shortwave will push some energy across these regions, which will support a broad area of widespread/numerous thunderstorms. With weakening steering flow and remnant MCVs from earlier convection, storm motions are expected to become very slow, which will heighten the threat of flash flooding. One of these MCVs may be producing ongoing heavy rainfall across the Ozarks and into northeast OK and southeast KS at the start of the Day 2 forecast period Monday morning, which prompted the upgrade to a Slight Risk here. By midday Monday and into the evening hours, the flash flooding risk is expected to span from WI/IL south- southeast to the southern Appalachians and Tennessee Valley. These numerous slow-moving thunderstorms are forecast to contain at least 2"/hr rates at times and create scattered instances of flash flooding. Then, a final round of efficient rain- producing thunderstorms may occur across the lower Ohio and Tennessee valleys near the southwest inflow sector of a potent MCV overnight Monday. Currently, there remains high uncertainty with the exact location of this feature, but CAMs depict the potential for 5-7" rainfall totals near western KY and western/middle TN. The HREF shows impressive neighborhood probabilities (40-60%) of 24-hr rainfall totals exceeding 5 inches in this region. Some of these areas within the Slight Risk will also receive heavy rainfall during the day 1 period, which may increase the risk of flash flooding if areas are impacted by additional storms with heavy rainfall on Monday. Isolated pockets of significant impacts are possible and these areas will be monitored for future upgrades should confidence in locations of extreme rainfall increase. Outside of the Slight Risk area, a broad Marginal Risk area extends into the Upper Midwest and central Plains. Anomalous moisture will surge north behind the lifting warm front, which will support locally heavy rainfall that may lead to isolated instances of flash flooding for the western Great Lakes states. Models have also started consistently showing a potential MCS forming underneath a potent upper level shortwave moving quickly east across the central Plains on Monday evening. Though this feature would likely be progressive, it could have the potential to produce heavy rainfall and isolated flash flooding. There is still some uncertainty regarding the location of this feature, resulting in a broad Marginal Risk area that will likely be narrowed down over the next few forecast cycles. Dolan/Snell Day 3 Valid 12Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE UPPER MIDWEST AND OHIO AND TENNESSEE VALLEYS... On Tuesday, an upper level trough will move across the northwestern U.S. and support cyclogenesis over the northern Plains. A wave of convection is expected to form ahead of the developing cyclone, bringing thunderstorms to much of the Upper Midwest. A moist and unstable air mass will be in place across the Upper Midwest after a warm front lifts north on Monday, which will support heavy rainfall in thunderstorms. Flash flood potential should be limited by the progressive nature of this system, but locally heavy rainfall could still lead to isolated instances of flash flooding, especially where soils will be moistened from rainfall expected on Sunday and Monday. A Marginal Risk area seems sufficient to cover the flash flood threat at this time. Another Marginal Risk area is in place for much of the Ohio and Tennessee Valleys and portions of Michigan where a slow moving frontal boundary will linger through Tuesday. This frontal boundary will provide modest lift/support for scattered convection across these regions. An anomalously moist air mass will still be in place, which should be enough to support locally heavy rain in some stronger storms and may lead to isolated instances of flash flooding. The flash flood threat will be significantly lower for these regions than on Monday with much weaker synoptic support. Dolan/Snell 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