FOUS30 KWBC 110133 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 933 PM EDT Wed Jun 10 2026 Day 1 Valid 01Z Thu Jun 11 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... An outflow boundary from earlier and current convection exists across portions of southwest IA and northeast MO. Storms forming in this area continue to have the potential to produce heavy downpours with hourly rainfall amounts up to 3" with local totals to 5", which would exceed declining flash flood guidance across this region. Storms forming further north along the front will also have the potential to produce locally heavy rainfall as well, particularly towards the end of the period/Thursday morning. A combination of radar reflectivity trends and trends in the 12z REFS/18z HREF led to some southern sag of the Slight Risk area and significant reduction of the Marginal Risk area across portions of MN, WI, and MI. ...Portions of New York and New England... A surface low pressure system will track across southeastern Canada and lift a warm front across the Northeast. Upper level troughing extending across the Northeast and Mid-Atlantic has allowed 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, which will allow for locally heavy rainfall with rates of 1-2 inches per hour particularly this evening across northeast NY and Central New England. Rainfall may also be enhanced by upslope flow into the terrain. The Marginal Risk has seen a bit of reduction due to radar reflectivity trends and trends in the 12z REFS/18z HREF guidance. ...Portions of Ohio, western Pennsylvania, and West Virginia... Returning moisture in an area of 2000-3000 J/kg of MLCAPE along with close to 25 kts of effective bulk shear has led to a couple random heavy rain cores across Lake Erie and near Akron OH. The mesoscale guidance showed a weak to modest signal for heavy rain in this region, but considering the recent heavy rains near Akron, felt it was prudent to add a Marginal Risk for portions of eastern OH, western PA, and WV where this signal was noticed. Hourly rain amounts to 2.5" would be possible on an isolated basis, which would be problematic over moderate to low flash flood guidance values. Roth 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 $$