004 FOUS30 KWBC 242028 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 428 PM EDT Fri Jul 24 2026 Day 1 Valid 16Z Fri Jul 24 2026 - 12Z Sat Jul 25 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST UNITED STATES... ...Southeast... A stalled front in the vicinity, draped across northern Georgia toward coastal North Carolina, will be the focus for scattered to numerous showers and thunderstorms during the period. Anomalous moisture, characterized by PWs in the 2.0-2.4 inch range, combined with building instability (mainly along the immediate coast), will support high rain rates. The latest guidance points toward potential for instantaneous rain rates in excess of 2-3"/hr, particularly from interior South Carolina toward the coast as well as portions of southeastern NC. Total amounts during the period may exceed 3-5 inches in localized areas. No significant changes were made to the Moderate Risk area, which covers the threat well for scattered to numerous instances of flash floods, some of which could be significant. ...Ozarks and Lower Missouri Valley... Convection may be ongoing at the start of the period somewhere across portions of eastern Kansas and Missouri. This activity should taper off as the nocturnal low level jet tapers off. There is more uncertainty about what happens later in the forecast period, from late this afternoon into tonight, Most hi-res models still suggest the convective cluster will progress southeast into the Ozarks and potentially Mid- Mississippi Valley by 12Z Saturday. However, they increasingly disagree on placement of the heaviest rainfall, the convective evolution, and magnitude of the rainfall. From a pattern recognition standpoint, there is some concern about an increasingly favorable setup for a backbuilding MCS overnight. The low-level jet will veer to be more westerly, and the 20-30 knot low-level inflow will exceed the strength of the increasingly weak 15-20 knot deep layer mean flow. Synoptic evolution would favor potential for backbuilding storms tonight, but that is contingent on the convective evolution and whether a stronger, more concentrated cold pool can develop. ...Southwest US... Another moisture abundant day in the southwest U.S. will lead to another round of isolated to widely scattered convection peaking this afternoon and lingering into the early overnight hours. No changes needed to the risk areas, with the threat covered well with the Marginal Risk. ...Northern Minnesota... A localized flash flood threat exists with an approaching front interacting with somewhat elevated moisture in place. The 12Z guidance points toward a stripe of locally heavy rainfall, potentially 1-3", across northern Minnesota, mainly interior areas. A Marginal Risk was introduced. Taylor/Bann/Lamers Day 2 Valid 12Z Sat Jul 25 2026 - 12Z Sun Jul 26 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE EASTERN CAROLINAS...PORTIONS OF ARKANSAS...AND THE SOUTHWEST... ...Southeast through the Tennessee Valley... Along and in the vicinity of the stalled frontal boundary, plentiful moisture will be in place. The main focus will be across the eastern Carolinas where guidance continues to point toward heavy rainfall continuing from the day one period. Hi-res guidance points to localized 2-4 inch totals with higher rain rates likely as well. The Slight Risk was maintained along the coastal areas for scattered instances of flash flooding. Over portions of Arkansas, the 12 UTC guidance today showed increasing agreement with a complex of thunderstorms developing Saturday with slow moving or repeating rounds of heavy rainfall. Across the board, there was a general uptick in the QPF totals with the HREF neighborhood probabilities for 3-5 inches above 80 percent. HREF and REFS probs also have trended higher for hourly totals in excess of 2-3" at times 12Z-18Z. Some concern for some very localized extreme rainfall given slow storm motions. For these reasons, a Slight Risk was introduced. ...Southwest... The monsoon will recharge/reset across the Four Corners on Saturday with an uptick in coverage and intensity of rainfall across the region. QPF amounts did trend up overall and PW values are above the 90th percentile. Guidance points toward a MCV in the vicinity becoming a key player in enhancing the rainfall and leading to greater/higher rain rates. The Slight Risk was maintained with some adjustments to the latest QPF and across west-central NM, the risk does lean toward the higher end of the Slight Risk probability range. Taylor/Bann Day 3 Valid 12Z Sun Jul 26 2026 - 12Z Mon Jul 27 2026 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL ACROSS THE FOUR CORNERS REGION...UPPER MIDWEST...AND PORTIONS OF FLORIDA... ...Four Corners States onto the Central Plains... Monsoonal flow from the Desert Southwest to the central Rockies continues into early next week. Precipitable water values and available instability will again support isolated to widely scattered thunderstorms capable of producing intense rain rates capable of producing flash flooding. A broad Marginal Risk was maintained this cycle, but future forecasts may need an embedded Slight Risk once predictability increases. ...Upper Midwest-Great Lakes-Ohio Valley-Interior Northeast... Global and AI guidance continue to show convectively-aided shortwave activity riding down the top side of the upper ridge axis over the western Dakota border in northwest flow. Some spatial uncertainty in where the heaviest rainfall may occur with a slight nudge toward southern Wisconsin this cycle. As a result, the Marginal Risk was adjusted some to account for this, with an extension to the east over portions of WI/IL. Otherwise, the inherited risk area is in good shape. Taylor/Bann Day 4 and Day 5 Valid 12Z Mon Jul 27 2026 - 12Z Wed Jul 29 2026 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL MONDAY AND TUESDAY ACROSS THE FOUR CORNERS STATES EXTENDING INTO THE CENTRAL PLAINS, AND THE GREAT LAKES AND OHIO VALLEY ON MONDAY SHIFTING TO THE NORTHEAST AND MID-ATLANTIC FOR TUESDAY... ...Four Corners States into the Central Plains... Monsoonal flow bringing elevated moisture over the Desert Southwest through the central Rockies continues with a southward trend in the upper high center directing activity back onto the central Plains early next week. Main edits for both Days 4/5 were to include in the Marginal Risk the typical terrain on the western end in northwest Arizona and Southwest Utah as well as farther downstream over the central Plains, especially for Day 5. EC-AIFS QPF and ECMWF PW anomaly plots continue to prove helpful in highlighting areas of increased concern (including coverage for the central Plains). The more suppressed ridge will allow greater shortwave passage over the top/across the Rockies. ...Great Lakes, Ohio Valley, Mid-Atlantic, and Northeast... The focus of shortwave activity rolling off the High Plains ridge axis is perhaps best depicted by the 12Z ECMWF as tracking over northern MN on Monday and developing into a low pressure system downstream of the Great Lakes on Tuesday. This low would provide the forcing for heavier rain and a potential Slight Risk over the Northeast, so that will need to be monitored. Otherwise, it's northwest flow progressive convective activity from the Great Lakes tracking to the Northeast with training where the flow is parallel to boundaries. The Marginal Risk for Day 4 was expanded back west over Chicago and Indiana while the Day 5 was trimmed a bit to hone in on the Mid-Atlantic through Northeast (perhaps not as much of Maine). The EC-AIFS proves helpful here too with the positioning of the areas as well as the last 12 hours of the 12Z RRFS/RDPS for the first half of Day 4. Jackson 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 $$