FOUS30 KWBC 081949 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 349 PM EDT Mon Jun 8 2026 Day 1 Valid 16Z Mon Jun 08 2026 - 12Z Tue Jun 09 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE OZARKS... 16Z Update... The inherited Moderate Risk area was dropped due to the MCS now exiting the region. A section of a new Slight Risk area was left over southwest MO as new thunderstorm activity flares up over southwest MO and far northwest AR. In collaboration with several Kansas WFOs, a Slight Risk was introduced for much of northern KS to account for the highly anticipated MCS that will traverse the Central Plains. Model soundings show anomalous PWs above 1.7" and soils from northern KS to eastern KS are more sensitive given recent rainfall (especially eastern KS). Progressive storm motions should limit the areal extent of the flash flood threat, however an acceleration in the low-level jet will intersect the southern flank of the MCS and could lead to back-building convection late tonight and into Tuesday AM. Latest 12Z HREF probabilities do show moderate chances (40-50%) for QPF totals >3" tonight and 30-50% chances for 3-hr QPF totals exceeding 3-hr FFGs. For these reasons, the Slight Risk was introduced in northern KS. In the Mid-South 12Z CAMS, HREF, and REFS guidance have all increased probabilities for >3" rainfall totals farther south into central AL and central GA. The air-mass is essentially a tropical air-mass, highlighted by the 12Z BMX sounding which measured a 2.18" PW, little-to-no capping inversion, and RAP forecasts depicting >1,000 MLCAPE. Weak synoptic-scale forcing will keep storms more hit-or-miss in nature, but persistent SWrly flow will provide some lift as it intersects the higher terrain in northern AL/GA. Soils are incredibly saturated with soil moisture topping the 95th percentile on NASA SPoRT-LIS in the 0-10cm and 0-40cm layers. Expanded the Slight Risk farther south, although the greatest concern for flash flooding is in northeast AL and northwest GA where soils are the most sensitive. Lastly, expanded the Slight Risk farther south into central WI. the potent and compact 850mb low in the Upper MS Valley will have PWs above the 99.5 climatological percentile at its disposal this afternoon and tonight. There is concern for organized clusters of storms to form and train over southwest WI that could contain max rainfall rates around 2"/hr. There is greater concern in this area given the 12Z HREF probabilities show moderate-to-high chances (50-70%) for rainfall totals >3". The areal coverage of the flash flood threat is not high enough to consider a Moderate Risk, but the setup still could support scattered instances of flash flooding this evening. Mullinax ---Previous Discussion--- Convection will be ongoing at the start of the period across the Ozarks where a low level jet ahead of a mid-level vortex/wave will create favorable convective conditions that will likely lead to impactful flash flooding, especially near steep terrain. During the early morning hours, hi-res CAMs are showing rainfall totals as high as 5-8 inches for portions of southeastern Kansas, northeastern Oklahoma, southwestern Missouri, and northwestern Arkansas where slow, back-building thunderstorms are expected. An anomalously moist and unstable air mass is already in place across the central U.S., which will support deep convection with highly efficient rainfall rates (rates of 2-3 inches per hour are already being observed). This region was incorporated in a special update Moderate Risk area overnight, and the Moderate Risk will continue into the beginning of the Day 1 period this morning. Convection should wane and shift southeast later this morning into this afternoon as the system becomes dominated by the outflow. The broader Slight Risk area includes much of the Middle Mississippi and Tennessee Valleys where widespread showers and thunderstorms are expected in the warm sector of a northern stream cyclone today. Much of the convective activity will be driven by mesoscale boundaries and remnant MCV activity continuing from the overnight period, which will result in variability of the QPE across the warm sector. Some convection may be more focused along a quasi-stationary frontal boundary draped over the Tennessee Valley and southern Appalachians. Convection will be enhanced by a leading upper level shortwave with embedded MCV activity that will push east across these regions, and the environment will be extremely supportive of heavy rainfall with high moisture (PWAT values around 2 inches) and high instability (MUCAPE greater than 3000 J/kg). Storms are expected to be slow moving due to a lack of steering flow, which will allow for locally high rainfall totals. Latest CAM guidance suggests rainfall rates up to 2-3 inches per hour and totals up to 5-8 inches will be possible over portions of the Middle Mississippi and Tennessee Valleys. HREF neighborhood probabilities show the highest chances of exceeding 5 inches of rainfall in 24 hours (25-45%) will be over an area from southern Illinois and Indiana through western Kentucky and Tennessee. These areas can expect impacts on the higher end of the Slight Risk category. Some of the areas within the Slight Risk received heavy rainfall on Sunday, which may increase the risk of flash flooding if areas are impacted by additional storms with heavy rainfall today. The Slight Risk areas has also been extended north into central Wisconsin and eastern Iowa where slow-moving storms are expected to be enhanced by a mid-level low this afternoon. Outside of the Slight Risk area, a broad Marginal Risk area extends into the Upper Midwest and central Plains where locally heavy rainfall may lead to isolated instances of flash flooding. Storms across much of the Upper Midwest should be fairly progressive, which will limit flash flood potential, but isolated flooding concerns will be possible if heavy rainfall impacts any urban areas. Models continue to also show a potential MCS forming underneath a potent upper level shortwave moving quickly east across the central Plains this evening. Though this feature would be very progressive, deep convection will have the potential to produce heavy rainfall and isolated flash flooding. This shortwave may also enhance convection again over the Middle Mississippi Valley tonight, and there could be a scenario where a targeted Moderate Risk area is needed. Dolan Day 2 Valid 12Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHERN PLAINS AND WESTERN KENTUCKY AND TENNESSEE... 20Z Update... The inherited threat areas in the Northern Plains and Upper Mississippi Valley were adjusted based on latest WPC QPF and 12Z HREF probabilistic guidance. The primary change this forecast cycle was to expand the Slight Risk in the Mid-South farther south and east into the TN Valley and southern Appalachians. Latest 12Z guidance has shown a gradual southward expansion in the QPF field, which aligns well with where the highest PWs (around 2.0" PWs) and instability will be located. A sheared 500mb trough tracking towards the Southeast will also promote healthy upscale ascent over an area with very sensitive soils. The 12Z HREF/REFS probabilistic guidance shows moderate-to-high chances (50-70%) for rainfall totals >3" in northern GA and parts of the western Carolinas. In addition, farther north, the same 12Z HREF/REFS guidance shows low chance probabilities (20-40%) in central KY and northern TN. These areas under what would be considered the "high-end Slight" section within the larger Slight Risk area in the Mid-South. CAMs guidance is more on the southern envelope of QPF rather than global models which are farther north. Still, some CAMs members show some locally significant rainfall totals where back-building and training storms occur. The northern Plains and Upper Mississippi Valley threat areas had minor adjustments based on latest guidance, but otherwise no additional threat areas were proposed this cycle. Mullinax ---Previous Discussion--- On Tuesday, a potent upper level trough will move across the northern Rockies and emerge into the northern Plains. This trough will spur cyclogenesis over the northern Plains while a low level jet increases moisture and instability ahead of the system. The environment will be ideal for supercell development Tuesday afternoon, and increasing shear over the region will allow storms to evolve into an MCS Tuesday evening into Tuesday night. Deep convection within these severe storms will be able to tap into moisture in the atmosphere (PWAT values 1.5-2 inches) and create very heavy rainfall. The quick nature of the MCS should somewhat limit the risk of flash flooding, but intense rainfall rates in excess of 2 inches per hour will exceed FFGs and could lead to impactful flash flooding, especially in urban areas. A Slight Risk area has been introduced for much of central and eastern North Dakota and northwestern Minnesota. Scattered showers and storms are forecast from the southern Appalachians and Tennessee Valley through the Ohio Valley and Great Lakes region, which will be supported by an upper level shortwave lifting northeast across the Ohio Valley and Great Lakes and a slow moving warm front extending south into the Tennessee Valley and southern Appalachians. The air mass in place will be anomalously moist (PWATs around 2 inches) and sufficiently unstable to support locally heavy rainfall. Available hi-res guidance suggests higher rainfall totals will be possible across western Kentucky and Tennessee where convection will continue from the Day 1 period into Tuesday morning. A mid-level shortwave will be enhancing this convection and should allow for efficient rainfall rates over 2 inches per hour. A Slight Risk area has been introduced to cover the elevated flash flood threat over western Kentucky and Tennessee. Global models have also been showing locally enhanced rainfall totals over portions of the Ohio Valley, but there is still a significant amount of uncertainty in the location of these higher totals. It is possible the Slight Risk area may need to be expanded to the northeast as convective details become more clear with additional hi-res guidance available later today. Dolan Day 3 Valid 12Z Wed Jun 10 2026 - 12Z Thu Jun 11 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN KANSAS INTO NORTHERN MISSOURI AND SOUTHERN IOWA... 20Z Update... The inherited risk areas remain in good shape and the rationale provided from the previous shift remains on track. Did adjust the Slight Risk a little farther south and west to account for typical QPF biases in global guidance that tend to be too far north. But otherwise, no significant changes were made this forecast cycle. Mullinax ---Previous Discussion--- On Wednesday, the northern Plains cyclone will be moving swiftly east and pushing a cold front across the Midwest. Showers and thunderstorms are expected ahead of and along the frontal boundary from the Midwest to the central Plains, which are encompassed by a Marginal Risk of excessive rainfall. The tail end of the front will likely hang up on the Rockies and flatten out over the central Plains, and low pressure is expected to develop over Kansas where a dryline will intersect the boundary. Models are showing impressive moisture transport ahead of the frontal boundary Wednesday morning and a secondary surge Wednesday night as a strong low level jet brings increasing moisture and instability into the central Plains. This set up will be conducive for heavy rainfall, and global models are showing potential for heightened rainfall totals of 2-4 inches within the Slight Risk area, which may be underdone given the convective limitations of the models. Locally heavy rainfall may also be possible over central Wisconsin and could impact areas highlighted with a Slight Risk on Day 2, which could warrant an additional Slight Risk upgrade. However, there is much more uncertainty regarding rainfall totals in Wisconsin, which may be limited by the progressive nature of the cold front. Dolan 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