777 FOUS30 KWBC 010835 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 435 AM EDT Sat Aug 1 2026 Day 1 Valid 12Z Sat Aug 01 2026 - 12Z Sun Aug 02 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE UPPER MIDWEST TO THE GULF COAST AND FOR NEW MEXICO INTO THE SOUTHERN HIGH PLAINS... ...Upper Midwest... A potent and unseasonably deep low pressure system will continue tracking across the Upper Midwest as its parent mid/upper low digs and deepens over the region. A steady influx of deep Gulf moisture will be pooling ahead of the system with PW values around 2-2.25 inches/150-175% of normal. Strong forcing, large scale ascent, and sufficient instability will all be present to lead to efficient,heavy rainfall especially within the pivoting comma head due north of the low track across parts of Illinois and Indiana where guidance has been suggesting a concentration of 3 to 5 inches. As a result, the existing Slight Risk spans the Midwest to the Tennessee Valley and the portion over east-central Illinois to northern Indiana can be considered an enhanced Slight. ...Parts of the Southeast to the Gulf Coast... A mid/upper impulse embedded within northwesterly flow on the southern periphery of the deepening low over the Upper Midwest will dive into the Southeast before slowing down near the Florida Panhandle during the Day. Anomalously high PW values of 2.25-2.75 inches (125-150% of normal) along with 1000-2000+ J/kg of MUCAPE will support numerous clusters of slow-moving showers and thunderstorms containing intense rainfall rates. Some of the hi-res guidance is favoring parts of Georgia and Florida for very localized pockets of 3+ inches (very isolated areas of 5+ inches). A Slight Risk covers much of the Florida Panhandle, eastern Alabama, most of Georgia, western half of South Carolina, and western North Carolina. ...Southern Rockies/High Plains to the Texas Hill Country... Monsoonal moisture and instability interacting with upslope flow and a southward progressing cold front will support scattered showers and thunderstorms from the Southern Rockies and High Plains to the Texas Hill Country. Individual storms could potentially drop 1+ inch/hr rainfall rates that may lead to isolated to scattered instances of flash flooding. The most favorable locations for this will be across eastern New Mexico into far western portions of Texas. A Slight Risk area remains in effect for this part of the region. There continues to be an increasing signal for multiple inches of rainfall to focus across the Hill Country. A broad Marginal Risk spans from southeast Arizona northward to southern Colorado and to the east of the Texas Hill Country. Campbell/Miller Day 2 Valid 12Z Sun Aug 02 2026 - 12Z Mon Aug 03 2026 ..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE FLORIDA BIG BEND REGION, AND OVER PORTIONS OF THE NORTHEAST... ...Gulf Coast into the Southeast... Onshore flow will continue to focus heavy rainfall over northern Florida and parts of the Southeast. The mid-level low over Indiana is forecast to move east/south allowing for height falls to reach the Gulf Coast and maintaining S/SW flow downstream. An impressive plume of PWs above 2.25" overlapped with MUCAPE of around 2000 J/kg will be pooled ahead of the approaching surface cold front, and it is this impressive environment that will shift northeast Thunderstorms will be widespread; training and backbuilding can be expected with hourly rates reaching 2 or more inches/hour. Several locations may accumulate 3+ inches/24 hours thus maintaining an elevated threat for flash flooding. ...Upper Midwest to Northeast and Mid-Atlantic region... A slow moving occluded front will be advancing eastward into the Ohio Valley. Impressive thermodynamic advection within the warm sector will surge northward as 30-40 kts of wind at 850mb transport PW values of 1.75 to 2.0 inches all the way to the Canadian Border overlapping 500-1000 J/kg of MUCAPE. This will support widespread thunderstorms with rainfall rates of 1-2"/hr, with organization into clusters fostered via 30-35 kts of bulk shear. With time, winds will become more parallel to the front which will increase the threat for training of cells from the Mid-Atlantic states northward into Upstate New York. The current Slight Risk is focused from eastern lower Michigan northeast towards the Adirondacks where an impressive deformation axis will develop and lay beneath a rare August-TROWAL to enhance both ascent and instability. Here, mean winds become anti-parallel to the propagation vectors, and it is likely that some slow moving/backbuilding cells will bring heavy rainfall to areas including Detroit, Cleveland, and Buffalo. This is where the greatest excessive rainfall risk exists and where the highest probabilities for rainfall exceeding 3"/24hrs. ...Southwest... Favorable instability and moisture will be a bit suppressed during this period thanks to the with the somewhat flattened ridge downstream. The anomalous PW values and SBCAPE above 1000 J/kg will generally be confined to the Mogollon Rim and southern vicinity. Convection is still likely to blossom across Arizona and New Mexico and storms that develop may organize slightly to move southwest off the terrain. A Marginal Risk area remains in effect for this period. Campbell/Weiss Day 3 Valid 12Z Mon Aug 03 2026 - 12Z Tue Aug 04 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE NORTHERN MID-ATLANTIC INTO SOUTHERN NEW YORK STATE AND SOUTHERN NEW ENGLAND... ...Portions of the East Coast and Ohio Valley... An axis of anomalous PW values, 2+ standard deviations above the mean, 2 to 2.25" PW values, will stretch from North Florida, northeastward across the coastal Southeast, Mid- Atlantic and from eastern New York State into New England will support locally heavy rainfall. A slight risk remains over portions of the northern Mid- Atlantic (including portions of NY) into southwest New England where recent heavy rains have lowered FFG values/saturated soils. During the day the closed low is forecast to slow/stall while maintaining an area of anomalous PW values east of this closed low, across the Upper Ohio Valley into the Mid- Atlantic, Southern New England and south into the coastal southern Mid-Atlantic. A broad marginal risk area was depicted in this anomalous PW axis for locally heavy rains and isolated runoff issues. ...Southwest/Southern High Plains... Convection will become less suppressed as the ridge builds to the east allowing for more monsoonal moisture and instability to reach the Southern Rockies/adjacent High Plains. Locally heavy rainfall with isolated runoff issues possible for this period. A Marginal Risk spans from southeast Arizona into New Mexico and south- central Colorado. ...Portions of the Central/Northern Plains and Midwest... Areal average of 1-2 inches expected as a surface front advances southeastward from the Upper Mississippi Valley into the Upper Lakes and south through the Central Plains. Moist southerly low level inflow into the front at this time may support organized convection, heavy rains and isolated runoff issues. A Marginal Risk is in affect for northern Minnesota, easter North Dakota and northeast South Dakota. Campbell/Roth Day 4 and Day 5 Valid 12Z Tue Aug 04 2026 - 12Z Thu Aug 06 2026 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FROM THE UPPER OHIO VALLEY/EASTERN LAKES INTO THE NORTHEAST, FROM THE CENTRAL PLAINS IN THE MID TO UPPER MISSISSIPPI VALLEY AND OVER THE SOUTHWEST... ...Upper OH Valley, Central Appalachians, Lower Lakes, Mid-Atlantic into the Northeast... Very little movement expected day 4 to the closed low in the vicinity of eastern KY/eastern TN, with then a northeastward push into the eastern lakes on Wednesday as it begins to weaken. A broad region of anomalous PW values will persist day 4 and day 5 to the east of this closed low from the Upper OH Valley, Central Appalachians, eastward into the Mid- Atlantic, much of NY State and southern New England. Confidence is low with qpf details, but there will likely be areas of heavy rains both day 4 and 5 across these areas with isolated runoff issues possible. Given the uncertainties with details, the risk level was kept at marginal for both day 4 and 5. ...Southwest/Southern High Plains... For both day 4 and 5, 1200 UTC Tuesday to 1200 UTC Thursday, a marginal risk was depicted for monsoonal convection across southern Arizona into New Mexico. Not a lot of confidence with qpf details here, but locally heavy rains and isolated runoff issues possible in the above average PW values expected across this area. ...Central Plains into the Mid to Upper MS Valley... A surface frontal boundary is expected to remain nearly stationary during the day 4 and day 5 time period from the Central Plains, east-northeastward into the Mid to Upper MS Valley region. This front will be situated along the southern edge of the westerlies where shortwave energy pushing east northeastward along the frontal zone will support potential for organized convection both day 4 and day 5. PW values expected to be slightly above average...1.5 to 1.75"+ in the vicinity of this front, supporting heavy precip totals where convection does organize and isolated runoff issues. Oravec 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 $$