FOUS30 KWBC 241554 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1154 AM 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 AND FOR PORTIONS OF NEW MEXICO... ...Southeast through the Tennessee Valley... The outlook for the Southeast was left fairly consistent with the previous version with a Slight Risk in the eastern Carolinas, and a broad Marginal Risk over the rest of the region in the general vicinity of the lingering front. Hi-resolution guidance has become more available and continues to place the heaviest rain farther south. For the time being, the Marginal Risk was positioned in an intermediate location and close to the corridor of greatest QPF and along the axis of highest precipitable water values. This also continued to align with the WPC deterministic forecast. However, the positioning of the risk area may continue to evolve in future outlook updates. Overall, the environment will still be favorable for high rain rates in the most organized thunderstorms, with precipitable water values still expected to be above 2 inches. ...Southwest... The monsoon recharges and resets across the Four Corners region on Saturday. A Slight Risk was introduced primarily across New Mexico where available high resolution convective allowing models showed localized heavy rainfall in the same area as elevated values approaching 20 percent on the 12Z CSU machine learning ERO probability guidance. There is some concern about the potential for a MCV from late tonight/early Saturday morning to become a player which elevates the potential for flash flooding later in the day on Saturday. This would be in addition to the precipitable water values that will continue to be around or just above the 90th percentile for July, and supportive of high rain rates in any thunderstorms that can develop. 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 STATES, EXTENDING INTO THE CENTRAL PLAINS MONDAY AND OVER THE GREAT LAKES, EXTENDING INTO THE NORTHEAST ON MONDAY... ...Four Corners States onto the Central Plains... Monsoonal flow from the Desert Southwest to the central Rockies continues into early next week. Precipitable water anomalies are offset with the ECMWF farther west (New Mexico and Colorado as compared to the GFS being located over Arizona and Nevada). Maintained the Marginal Risks but will continue to note that shortwave impulses coming up from Mexico could enhance precip and warrant a Slight Risk. Was able to remove part of southwest WY given confidence on anomalous moisture being contained south from the Uinta Mtns. ...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. There was a bit of a realignment made which focused on the shortwave crossing the southern portion of Minnesota and Iowa moreso than the area farther north. In doing so...the QPF tracks along a corridor of lower Flash Flood Guidance that reaches 1.5 inches per 3 hours and tends to fit the placement of maximum precipitable water values which peak at or slightly greater than 1.75 inches. The convection should be progressive enough to preclude the need for a Slight Risk at this point. 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 OVER THE EASTERN GREAT LAKES AND OHIO VALLEY EXTENDING INTO THE NORTHEAST AND MID ATLANTIC... ...Four Corners States into the Central Plains... Monsoonal flow from the Desert Southwest to the central Rockies and central Plains continues into early next week. Based on the latest (00Z) guidance, did not make many changes to yesterday's Day 5 Marginal Risk area. This also includes the latest ECENS/GEFS/CMCE 24 probabilities of 1-2+ inches in 24 hours. For Day 5 (12Z Tue-12Z Wed), given the persistent pattern, the ERO is essentially a carbon-copy of Day 4, with the eastern extension across the Central Plains. This follows along with the boost in QPF per the AIGFS and ECMWF AIFS, as both of these models show more vigorous (convectively-induced or enhanced) shortwave activity rounding overtop the mid/upper level ridge. ...Eastern 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. Guidance still shows these ridge crawlers becoming a bit better organized through the day 4-5 period, with an uptick in deep-layer QG forcing (Qs convergence) and increasing low-level moisture transport. By Day 5, strengthening exit region forcing downwind of advancing upper level jet streak will help amplify the longwave trough across the Great Lakes-OH Valley and Northeast, with a decent surge in pre-frontal deep-layer moisture as PWs climb between 1.75-2.00". Based on the QPF trends from the global guidance (including AI), and given the progressive forward speed of the embedded shortwaves, have essentially propagated the Day 4 Marginal farther downstream into the Eastern Seaboard from the Mid Atlantic to Northeast Tue into Wed. Given the progressive nature of the synoptic features, relatively low 24hr probabilities of QPF>2" per the GEFS/CMCE/ECENS systems, and current lackluster ECMWF EFI values, for now will start with a broad Marginal Risk, though with the anticipation that at some point (once in the short range) we may be able to target areas with a notably higher ERO risk (i.e. Slight). Hurley 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 $$