540 FOUS30 KWBC 120030 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 830 PM EDT Thu Jun 11 2026 Day 1 Valid 01Z Fri Jun 12 2026 - 12Z Fri Jun 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST... 01Z Update... Main changes were limited to removing areas where convective has exited in the Upper Midwest/Great Lakes and in parts of New York of Pennsylvania. Heavy rainfall was still being produced by convection making its way across the southern Great Lakes into parts of the Mid-Mississippi Valley where deep moisture remained in place ahead of an advancing cold front and a jet streak aloft was providing good upper level support. In the eastern US from parts of southern New York into the Mid- Atlantic region...locally heavy rainfall could still result in isolated instances for flooding. However...the threat is being mitigated by progressive forward speed of the storms and by the loss of daytime heating. Bann 16Z update... Several locations picked up 1 to 4 inches of rain overnight for the Midwest/Upper Midwest with the organized convection; prolonging the multi-day wet pattern for much of Iowa and ongoing areal flooding. Training and backbuilding of thunderstorms are expected to persist during the afternoon and into the evening hours for parts of Iowa and Illinois which will keep an elevated threat for scattered flash flooding while another round of convection lifts northeast into Wisconsin and Michigan with hourly rainfall rates. The Slight Risk area was expanded northward along the northern boundary in Wisconsin and lower Michigan. Refer to WPC MPD 384 for additional details. Campbell Early this morning, a frontal wave developed over the central Plains ahead of a strong upper level trough that will lift into the Midwest today. This wave of low pressure is forecast to surge northeast into the Midwest and be accompanied by an area of enhanced convection in the vicinity of the low. A strengthening low level jet on the leading edge of this disturbance will bring a surge of moisture (PWAT values > 2 inches) and instability (MUCAPE > 3000 J/kg) into the Midwest and create a sheared environment that will allow for organized convection with highly efficient rainfall rates up to 2-4 inches per hour. A Slight Risk of excessive rainfall is in effect for portions of the Midwest where the hi-res CAMs are showing the highest rainfall totals. There was some consideration of upgrading to a Moderate Risk for portions of Iowa, Wisconsin, and Illinois given recent heavy rains and soil saturation, but the highest rainfall totals today are forecast to be displaced to the north of where the heaviest rain fell on Wednesday, which should keep the risk of flash flooding more in line with a high-end Slight. On the backside of the frontal wave, the cold front will surge southeast across the central and southern Plains this afternoon with showers and storms expected to form along the front. Given the highly moist and unstable environment on the warm side of the boundary, these storms will be capable of producing high rainfall rates, but the progressive nature of the front should help limit the risk of flash flooding. A Marginal Risk area extends back into the southern Plains where locally heavy rainfall may lead to isolated instances of flash flooding. .Ohio Valley to Mid-Atlantic... An upper level shortwave trough is expected to move southeast across the Ohio Valley and Mid-Atlantic today, which will provide upper level support for the development of scattered showers and storms this afternoon. Warm, moist air will be in place across these regions, with PWAT values generally ranging from 1.75-2 inches, which will support rainfall rates of 1-2 inches. Elevated instability (>2000 J/kg) should allow for some deeper convective cells that will be capable of producing locally heavy rainfall. Isolated instances of flash flooding will be possible, especially if heavy rain occurs in urban environments, so there is a Marginal Risk of excessive rainfall extending from the Ohio Valley to the Mid-Atlantic. Northwesterly upslope flow will also result in enhanced precipitation totals along the central Appalachians that could create isolated flooding concerns in this region as well, which is included in the Marginal Risk area. .Southwest Florida... Southeasterly flow has increased PWAT values above 2 inches across Central and South Florida, which will allow for very heavy rainfall rates of 2-4 inches per hour in convection along the sea breeze boundaries this afternoon. Hi-res CAMs show the Atlantic and Gulf sea breezes colliding over Southwest Florida, which could result in flash flooding concerns for urban areas. Therefore, there is a Marginal Risk of excessive rainfall for urban areas along the west coast of the Florida Peninsula from Tampa south. Dolan Day 2 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 NORTHEAST AND FOR CENTRAL AND SOUTHWEST FLORIDA... 21Z update... The latest guidance had an uptick in QPF across portions of southern Florida in association with the seabreeze induced convection on the western side of the peninsula. This warranted a minor reshaping of the southern bounds of the Marginal Risk currently in effect. Elsewhere... there will be potential for heavy rainfall all along the draped frontal boundary from the Northeast/Mid-Atlantic region and westward to the Southern/Central Plains. Some areas have have recent rain to lower local FFGs which increase the risk for isolated areas of flooding concerns. No changes were made with this update for this part of the country. Campbell On Friday, an upper level trough will push across the Northeast and drive a cold front across the eastern and south-central United States. Scattered showers and storms are expected to develop as the frontal boundary interacts with the anomalously warm and moist air mass, and increased shear in the vicinity of the trough will likely support some deeper organized convection in portions of the Mid-Atlantic and Northeast. Moisture will pool ahead of the front, and PWAT values are forecast to rise above 2 inches from the southern Plains to the Northeast, which will allow for efficient rainfall rates. Flash flood potential should be somewhat limited by the speed of the front; however, locally heavy rainfall may lead to isolated instances of flash flooding. Storms over the southern Plains will move slower as the frontal boundary becomes quasi- stationary, which may result in some areas of higher rainfall totals. A mid-level wave is expected to move east across the central/southern Plains Friday evening, which should lift the frontal boundary north as a warm front and support a wave of enhanced convection Friday night. There is still quite a bit of uncertainty in where this area of convection will develop, but there will likely be some enhanced flash flood potential over portions of the central/southern Plains. Further southwest, southeasterly flow and increasing moisture will support enhanced showers and storms over West Texas and eastern New Mexico, which may create flooding concerns in the vicinity of the Guadalupe and Sacramento mountains and in burn scar areas. A Marginal Risk of excessive rainfall stretches from the southern Plains to the Northeast to cover these threats. Elsewhere, heavy rainfall will also be possible in Florida where anomalous moisture will reside. Convection along the sea breezes will have the potential to produce very heavy rainfall that could lead to flooding concerns for urban areas in Central and Southwest Florida. A Marginal Risk area has been introduced to cover these threats. Dolan Day 3 Valid 12Z Sat Jun 13 2026 - 12Z Sun Jun 14 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL PLAINS AND MID/LOWER MISSISSIPPI VALLEY... 21Z update... There is a growing signal for a concentration of areal average QPF of 3-5 inches to focus in the vicinity of eastern Kansas/Oklahoma and southwest Misouri, with the potential for very isolated maximums greater than 5 inches. This part of the region will likely be on the higher end of the Slight Risk threat for this period with more instances of flooding. Elsewhere, the latest QPF trends reflect the areas highlighted by the Marginal Risk already in place therefore no changes were necessary at this time. Campbell On Saturday, several features will come together to support a heavy rainfall threat over the central United States. An upper level trough will drop south into the central U.S. while several southern stream waves move northeast into the Plains ahead of this feature. At the surface, a warm front will lift across the south-central U.S. while a cold front moves south across the north-central U.S., creating an area of strong convergence from the central Plains to the Mid/Lower Mississippi Valley. In addition to strong synoptic forcing, a very warm, moist, and unstable air mass will be in place, which will support the development of numerous showers and storms with efficient rainfall rates. These features should stall for a period as they come together, resulting in an area of very heavy rainfall. A Slight Risk is in effect where the heaviest rainfall totals are expected from the central Plains to the Mid/Lower Mississippi Valley. Locally heavy rainfall will also be possible in showers and storms forming along the cold front in the Midwest, and isolated flash flooding will be a concern, especially after heavy rainfall expected on Day 1/Thursday. Locally heavy rainfall may also be possible across West Texas and eastern New Mexico where southeasterly flow may support terrain induced precipitation. A Marginal Risk of excessive rainfall surrounds the Slight and extends from West Texas and eastern New Mexico to the Great Lakes. Dolan Day 4 and Day 5 Valid 12Z Sun Jun 14 2026 - 12Z Tue Jun 16 2026 ...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND THE SOUTHEAST... The dayshift guidance continued to support the previous set of model runs by showing a broad, amplifying trough prevailing over over much of the eastern two-thirds of the CONUS this period. As shortwave energy drops into the base of broad trough and further amplifies it, the associated frontal boundary is expected to push well south into the southern Plains and lower Mississippi Valley on Sunday. Height falls aloft tied to the amplification leads to increasing southerly flow and moisture advection from the western Gulf will support deepening moisture along and ahead of the front. At the same time, upper level jet dynamics and mid- level energy provide areas of enhanced ascent. Coinciding with the deepest moisture (PWs at or above 2 inches) and some of the better forcing, a Slight Risk was maintained on Day 4 from southeastern Oklahoma and northeastern Texas over to central Mississippi. Farther north, an upslope component to the low level flow interacting with mid level energy dropping into the broader scale trough is expected to help initiate storms capable of producing locally heavy amounts and isolated flash flooding concerns as far north as the Colorado Rockies. By Monday, the front is expected to move more slowly to the south and east. As it does, moisture will continue to pool along the boundary, with both the GFS and ECMWF showing PWs increasing to over 2.25 inches (more than 2.5 std dev above normal) from South Texas to southern Alabama. Given the potential highly- efficient rainfall production and for the potential of training showers and thunderstorms, heavy amounts and flash flooding will be a likely concern across this area. A Slight Risk was drawn where the latest guidance showed the greater overlap between the deeper moisture and better forcing. Will continue to monitor this area for potential upgrades, especially if the model signal for heavy amounts continues to increase or show successive days of heavy rainfall across the same areas. Pereira/Bann 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 $$