739 FOUS30 KWBC 310819 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 419 AM EDT Fri Jul 31 2026 Day 1 Valid 12Z Fri Jul 31 2026 - 12Z Sat Aug 01 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF MID TO UPPER MISSISSIPPI VALLEY AND VICINITY... ...Central US system... Ridging across Montana and the Canadian Prairie will direct shortwave energy southeastward spreading showers and thunderstorms through the north-central and central states during this period. Moisture (2"+ & 99th+ percentile PWATs) will be sufficient enough to produce efficient rain rates, however, higher instability may not make its way far enough north to help realize higher rates. Flash flood guidance around 1" will allow for any convection/heavy rainfall to potentially produce flash flooding. A Slight Risk area encompasses southeast Minnesota, southern Wisconsin, Illinois, western Indiana, northwest Kentucky, eastern Missouri and central/eastern Iowa. The southern portion of the Marginal risk area remained closer to the placement of greater instability which would support higher intensity rainfall rates. Any downpours across that region may at least have a chance at challenging the flash flood guidance. ...Central Gulf Coast Region into parts of the Southeast... A quasi-stationary front will be orientated in the west-east fashion across the Gulf Coast region and will be a focus for locally heavy to excessive rainfall. Deep- layer moisture and instability should be more than sufficient and the guidance shows sufficient effective bulk shear (0-6km magnitudes generally over 20 kts) for more organized/persistent convective organization. ...Four Corners States into the Southern-Central High Plains... Monsoonal flow and anomalous deep-layer moisture will keep the potential for isolated instances of excessive rainfall across portions of eastern Arizona and much of New Mexico into Colorado. The areal coverage may be less than in preceding days given the expansion of the sprawling upper ridge. Diurnal monsoonal convection that develops over northeastern New Mexico is expected to dive south and generate isolated to scattered flash flooding in eastern portions of the state. Campbell/Bann Day 2 Valid 12Z Sat Aug 01 2026 - 12Z Sun Aug 02 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FRIDAY ACROSS PARTS OF THE UPPER MIDWEST TO MID MISSISSIPPI VALLEY... ...Ohio/Tennessee Valley... A potent low pressure system will supply plentiful instability to the Great Lakes/Ohio and Tennessee Valleys region beneath a deepening positively tilted mid-level low. PW values of 2+ standard deviations above average (2-2.25 inches) will be advecting into the region to support enhanced rainfall. A Slight Risk remains in effect from eastern Illinois to Ohio and southward to Alabama and Georgia. A broad Marginal Risk spans from Wisconsin to western New York south to the eastern Gulf Coast and Southeast. ...Central Gulf Coast Region into parts of the Southeast... Heavy rainfall threat will continue over this region along the southern periphery of the full-latitude trough, south of the quasi-sationary front. Deep-layer moisture and instability should be more than sufficient, especially when coinciding with the weak upper forcing (upstream upper trough w/ embedded convectively-aided shortwaves), for more organized/persistent convective organization. ...New Mexico... During this period general storm motion is expected to be from north to south into an increasingly moist environment (1"+ and 97.5th percentile PWATs) and relatively saturated soils from Friday storms will contribute to the flash flooding threat. A Slight Risk was maintained for portions of central/eastern New Mexico with a Marginal Risk area stretching from southeast Arizona to western Texas and northward to southern Colorado. Campbell/Kebede Day 3 Valid 12Z Sun Aug 02 2026 - 12Z Mon Aug 03 2026 ..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE NORTHEAST... ...Upper Midwest to Northeast and Mid-Atlantic region... The potent mid-level cyclone will continue to track to the east during this period ushering the showers and thunderstorms along with it into the Lower Great Lakes and Northeast region. Streaks of heavy rainfall are also expected to develop across parts of the Mid-Atlantic/North Carolina region. Some of these cells will have the potential to yield 2 inches over a short period during the afternoon and evening hours. A broad Marginal Risk spans from the North/South Carolina border northward to New York and Lower Michigan. A Slight Risk area covers extreme southeast Michigan, northeast Ohio, northern West Virginia, western Pennsylvania and western New York. ...Southeast... Showers and thunderstorms will persist along the stalled frontal boundary thus maintaining an elevated threat for heavy rainfall and potential for local flash flooding. Therefore, a Marginal RIsk area was maintained for eastern Gulf Coast/northern Florida and southern Georgia. ...Southwest... Monsoonal moisture will continue to drive convection across portions of New Mexico and Arizona. Locally heavy rainfall may continue to result in isolated flash flooding across the region. A Marginal Risk area is in effect for southern Arizona and southwest New Mexico. Campbell Day 4 and Day 5 Valid 12Z Mon Aug 03 2026 - 12Z Wed Aug 05 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE NORTHERN MID ATLANTIC INTO SOUTHERN NEW YORK STATE AND SOUTHERN NEW ENGLAND... The well defined upper trof moving through the Ohio Valley day 3, will begin to split into two pieces day 4. While there are differences with the details with this upper trof evolution, there is agreement that 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 NY State into New England. Generally favorable right entrance region jet dynamics will accentuate lift in this anomalous PW axis, supporting potential for locally heavy rainfall totals. A slight risk was added over portions of the northern Mid-Atlantic into southern NY State and southern New England where recent heavy rains have lowered FFG values. A marginal risk extends southward through the remainder of the Mid- Atlantic into the Southeast where locally heavy rains are also likely but FFG values are higher. For both day 4 and day 5...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. Day 5...the closed low over the Upper OH Valley will become nearly stationary day 5. An area of anomalous PW values will remain to the east of this closed low, across the Upper OH 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. The surface front moving through New England day 4, may become stationary and west to east oriented across southern New England into the northern Mid-Atlantic day 5. A few models are showing more defined heavy rains in the vicinity of this front where there is potential for persistent south southwesterly inflow. Still a lot of spread with qpf details, warranting only a marginal risk at this time, with changes possible with future updates. A surface front expected to push southeastward day 5 from the Upper MS Valley into the Upper Lakes and south through the Central Plains. There is model consensus for an axis of potentially heavy rains from Nebraska, eastward into Iowa and southern MN where the front may become more west to east oriented late Tue into early Wed. Moist southerly low level inflow into the front at this time may support organized convection, heavy rains 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 $$