FOUS30 KWBC 101906 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 306 PM EDT Wed Jun 10 2026 Day 1 Valid 16Z Wed Jun 10 2026 - 12Z Thu Jun 11 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL PLAINS AND MIDWEST... ...Midwest and Central Plains... 16z update... No major changes to the previous slight or marginal risk areas, but short term convective models are showing a better signal from northern Missouri into southern Iowa and northwest Illinois for training this afternoon and evening along the frontal boundary as it moves through and slows across the region. Earlier and ongoing convection in this area this morning will prime soils for later activity increasing confidence in flash flooding instances. Given some uncertainty, a moderate upgrade is not proposed at this time, but it is not out of the question for the later Day 1 update if the models continue to show a strong signal and better agreement. Maintaining a higher end slight for this particular area. --Santorelli Previous discussion... A strengthening cyclone will be moving northeast into south- central Canada and push a cold front across the north- central United States, which will trigger scattered showers and thunderstorms ahead of and along the front. A warm front will lift north ahead of the system, establishing a broad warm sector from the central Plains to the Upper Midwest. The warm sector air mass will be characterized by anomalously high moisture content, with PWAT values rising to 1.75-2.25 inches. Increasing temperatures and moisture will also result in increasing instability, with the highest MUCAPE (> 3000 J/kg) expected to concentrate over eastern Kansas, northern Missouri and eastern Iowa. Storms forming in this area will have the potential to produce heavy downpours with rainfall rates of 2-3 inches per hour, which would exceed FFG in much of this region. Storms forming further north along the front will also have the potential to produce locally heavy rainfall as well. Instability should be sufficient for deep convection across portions of Minnesota, Wisconsin, and Illinois, and convection may become more organized this afternoon with increasing shear along the frontal boundary. There remains some uncertainty regarding where the heaviest rainfall totals will be, but the HREF and RRFS generally agree on an area of elevated totals from northern Illinois through Wisconsin. This area will likely receive some locally heavy rainfall this morning from an eastward propagating MCS out ahead of the surface frontal boundary, then another wave of convection should ignite across the region this afternoon as the front approaches. For the central Plains, rainfall totals have generally trended downwards over the past 48 hours, most likely due to a more progressive frontal boundary that is oriented SW-NE instead of W-E, reducing convergence across the region. The synoptic setup should become more conducive for heavy rainfall over the central Plains late tonight into early Thursday as a frontal wave develops along the boundary and triggers an area of enhanced convection. Moisture and instability will surge into the central Plains ahead of this feature as a low level jet strengthens, which should support efficient rainfall rates in excess of 2 inches per hour. For these reasons, a Slight Risk of excessive rainfall extends from northeastern Kansas and southeastern Nebraska to Wisconsin and northern Illinois with a broader Marginal Risk area across much of the east-central Plains and Midwest. ...Tennessee Valley and southern Appalachians... 16z update... trimmed the western edge of this area where rainfall has ended, though scattered convection may fire up again this afternoon across western North Carolina and vicinity so maintaining the marginal risk for that region. --Santorelli Previous discussion... An MCS is currently moving southeast across the Ohio Valley and should move across the eastern Tennessee Valley and southern Appalachians this morning. Rainfall rates up to 2-3 inches per hour have been observed with this system overnight and will remain possible as the system moves across eastern Kentucky. Convection should weaken as the system is disrupted by the southern Appalachians, but upslope flow may enhance rainfall totals over the western Carolinas and western Virginia. Models have trended more to the northeast with this MCS, resulting in a shift in the Marginal Risk area, trimming out central Kentucky and most of western Tennessee and expanding into western Virginia. Luckily, rainfall from this system should be displaced from where heavy rainfall was observed yesterday over central and western Kentucky, but locally heavy rainfall may still lead to isolated instances of flash flooding. ...Interior Northeast and Mid-Atlantic... A surface low pressure system will track across southeastern Canada today and lift a warm front across the Northeast. Upper level troughing extending across the Northeast and Mid-Atlantic will allow for a region of broad ascent that will support scattered showers and thunderstorms. An anomalously moist air mass will push into these regions behind the front, increasing PWAT values up to around 2 inches (above the climatological 90th percentile), which will allow for locally heavy rainfall with rates of 1-2 inches per hour. Rainfall may also be enhanced by upslope flow over the terrain in the Interior Northeast and central Appalachians. A Marginal Risk of excessive rainfall covers portions of the Interior Northeast, central Appalachians, Mid-Atlantic where isolated instances of flash flooding will be possible. ...Southwest Florida... Convection will ignite as the Atlantic and Gulf sea breezes collide this afternoon over Southwest Florida. Southeasterly flow will increase PWAT values across the Florida peninsula throughout the day today, with the highest values (2.2-2.5 inches) focused over South Florida. Given a very moist atmosphere with strong convective forcing at the surface, thunderstorms will be able to produce heavy rainfall rates. The latest HREF is showing high probabilities (50-70%) of rainfall rates exceeding 2 inches per hour, and hi-res CAMs suggest rainfall rates of 3-4 inches will be possible in deeper convective cells. Rainfall rates this high will likely create localized flooding concerns for urban areas in Southwest Florida where there is a Marginal Risk of excessive rainfall. Dolan Day 2 Valid 12Z Thu Jun 11 2026 - 12Z Fri Jun 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST... ...Southern Plains to Midwest... The frontal wave that develops over the central Plains Wednesday night will surge northeast and intensify as a strong trough swings across the north-central United States. Strong southerly flow ahead of this wave will drive an anomalously moist and highly unstable air mass into the Midwest that will support enhanced convection in the vicinity of the frontal wave. Showers and storms will also form along the frontal boundary as it progresses, extending back into the southern Plains, but the progressive nature of the front should somewhat limit the flash flood potential over the Plains. Moisture will pool ahead of the cold front as it surges southeastward, creating a swath of high PWAT values of 2-2.5 inches from the southern Plains to the Great Lakes that will support high rainfall rates in excess of 2 inches per hour. Available CAMs and global models show a broad area of heavy rainfall across the Midwest, which is encompassed by a Slight Risk of excessive rainfall, and the highest rainfall totals are expected to focus over eastern Iowa, northern Illinois, and southern Wisconsin. A heavy rainfall/flash flood threat expected Wednesday evening/in the Day 1 period across this same region will make this area more susceptible to flash flooding in the Day 2/Thursday period. For now, maintaining a higher end slight risk, though an upgrade to a moderate risk in future issuances is not out of the question and very much dependent on what materializes across this region Wednesday evening. A larger Marginal Risk area stretches from the Midwest to the southern Plains where heavy rain may lead to isolated instances of flash flooding. ...Central Appalachians and Northeast... An upper level shortwave trough is forecast to move southeast over the Ohio Valley, Northeast, central Appalachians, and Mid- Atlantic, which will trigger another round of scattered showers and thunderstorms on Thursday. An anomalously warm and moist air mass will be in place across these regions, with PWAT values of 1.75-2 inches, which will support rainfall rates of 1-2 inches per hour. The upper level shortwave will result in an increasingly sheared environment over the Northeast Thursday afternoon, which will allow for some organized convection with higher rainfall rates in excess of 2 inches per hour. These storms should move quickly, but intense rainfall rates will support a risk of at least isolated instances of flash flooding for portions of eastern Pennsylvania, northern New Jersey, southern/central New York, and Connecticut where a Marginal Risk of excessive rainfall continues. Another Marginal Risk area remains in place over the central Appalachians from West Virginia into southwestern Pennsylvania where persistent northwesterly upslope flow will support enhanced precipitation chances in this area. Soils will be somewhat saturated from rainfall expected in the Day 1 period, and isolated flooding concerns may continue into Thursday with showers and storms capable of producing rainfall rates of 1-2 inches per hour. ...Southwest Florida... The pattern remains favorable in the Day 2/Thursday period for colliding Atlantic/Gulf sea breezes within a deep moisture flow. PWAT values in excess of 2 inches, along with sufficient instability, will support convection capable of producing heavy rainfall. This will be a quite localized threat, with flash flood potential focused over the mainly urban areas. With a similar setup expected in the Day 1 period, went ahead and introduced a Marginal Risk across Southwest Florida. Dolan/Santorelli Day 3 Valid 12Z Fri Jun 12 2026 - 12Z Sat Jun 13 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE SOUTHERN PLAINS TO THE NORTHERN MID-ATLANTIC... A low pressure system tracking across Canada will push a cold front across the eastern and south-central United States on Friday. As the frontal boundary interacts with the anomalously warm and moist air mass in place across the South and East, scattered to numerous showers and storms are expected to develop. PWAT values around 2 inches will stretch from the southern Plains to the northern Mid- Atlantic, which should support efficient rainfall rates. High shear in the vicinity of the upper level trough over the Northeast and northern Mid-Atlantic will likely allow for some strong, organized convection with the potential to produce heavy downpours. Storm motion across the East should be relatively quick given the progressive nature of the front, but this will be the third consecutive day of active convection for this region, which will support a risk of at least isolated flash flooding. The tail end of the front will become quasi-stationary over the southern Plains with broad southeasterly flow on the southern side of the boundary. Warm and moist air will support convection with locally heavy rainfall along the front, and convection may be enhanced Friday evening as an upper level shortwave moves east across the southern Plains. Showers and storms will likely extend west into New Mexico where precipitation chances may be enhanced near the Guadalupe and Sacramento Mountains. Locally heavy rainfall could also pose a flood risk for burn scars in eastern New Mexico. A Marginal Risk of excessive rainfall stretches from the southern Plains to the northern Mid-Atlantic along the boundary to cover these threats. Dolan/Santorelli Day 4 and Day 5 Valid 12Z Sat Jun 13 2026 - 12Z Mon Jun 15 2026 ...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE MIDWEST, SOUTHERN PLAINS, & LOWER MISSISSIPPI VALLEY... The general flow pattern features an unusually large trough for June developing and increasingly extending south to southwest from Ontario into the Southern Plains with time downstream of ridging building and shifting into the Pacific Northwest. Moisture, effective bulk shear, and instability is expected to be sufficient for organized convection near and ahead of a front which moves south through the region. Any waves along this front caused by shortwaves or jet streaks aloft would help focus organized convection. Given the general flow pattern, any mid- level cap should be weak and not prohibitive from a convective standpoint. Because of the relative lack of a cap, there is concern that these areas depicted for this weekend could trend south with time -- the available guidance in some areas led to a southward nudge from continuity. Overall, the risk areas and threat levels remain similar to continuity due to the lingering and typical uncertainty at this time range. Roth 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 $$