890 FOUS30 KWBC 050016 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 816 PM EDT Thu Jun 4 2026 Day 1 Valid 01Z Fri Jun 05 2026 - 12Z Fri Jun 05 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER A PORTION OF THE CENTRAL PLAINS AND MIDWEST... 01Z Update: The most prominent area for flash flooding will continue to reside across portions of the Central Plains into the Midwest with the axis lying between northeast KS into southwestern IA and areas in-between. Enhanced low-level convergence within the confines of a surface trough analyzed across the region will continue to be a driver for the heavy rainfall footprint located within the aforementioned zone. The southwestern edge of the convective field will likely have the greatest potential for rate driven excessive rains as the most consequential MLCAPE resides over eastern KS (750-1500 J/kg) compared to just ~500 J/kg further north into IA. That said, the area where the mean flow becomes a bit less meridional and provides a better back-building scenario lies across the quad-state intersection between IA/MO/KS/NE, the area where a majority of CAMs are highlighting the heaviest precip. Cold pool mergers and outflow propagation over central IA will likely generate quicker cell motions, thus limiting the threat for repeated impacts and/or training compared to areas further south. The SLGT risk exists over where the heaviest HREF mean QPF for the rest of the forecast is noted, as well as aligning within the surface trough placement that is anticipated to be a focus for the heavier precip orientation/potential. A MRGL risk also exists across the Northern Plains encompassing SD to western MN. Shortwave trajectory out of the High Plains of WY into SD will translate into a threat for severe thunderstorms of supercell characteristics this evening which point to a potential for at least isolated flash flood concerns over any areas impacted. The cell motions will likely limit the flash flood capabilities enough to not see scattered to widespread instances, but there's enough of a signal to maintain the MRGL risk that was in place through the initial forecast updates. This allowed for part of the MRGL over the North-Central U.S. to be maintained. A second MRGL risk is also maintained over southwest and west TX where bouts of heavy thunderstorms will be possible over the Caprock area, as well as down closer to the Big Bend. Models are all over the place with the convective evolution in these parts, but the ones that do produce are pretty hefty given the current environment in place. Best chance likely occurs over the Big Bend area down into the central RGV, stemming from a shortwave ejection out of Mexico that could very well bring strong thunderstorms out of the adjacent Mexican state of Coahuila. Plentiful SBCAPE with rich deep layer moisture reside within the confines of the river valley along the border, so the prospects for any storm to display significant rainfall rates is higher than normal. This was enough for a general maintenance of the MRGL risk in these areas. Kleebauer Day 2 Valid 12Z Fri Jun 05 2026 - 12Z Sat Jun 06 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF EASTERN NEBRASKA INTO THE MID-MISSISSIPPI VALLEY... ...21Z Outlook Update... The Slight Risk in the previous D2 issuance has been shifted southwestward and expanded slightly based on most recent model trends. Fairly progressive convection should migrate across much of Wisconsin and Lower Michigan in the morning/early afternoon hours. During the latter parts of the forecast period (afternoon onward), Additional, surface-based convection should redevelop near the NE/IA border and migrate eastward toward the MS River/IA/IL border region. This convection should be oriented favorably for local training/backbuilding - and some of that convection (particularly in Iowa) could fall on wet soils from prior-day anticipated rainfall, creating more moist ground conditions favoring excessive runoff. The current configuration of Slight reflects most recent model depictions of heavy rainfall risk from deep convection. Elsewhere, the overall forecast is generally on track, with small spatial expansions of Marginal in New Mexico to account for potential convection in higher terrain. Scattered thunderstorms should move slowly across the entire Marginal Risk area from NM/west Texas eastward to southeast Texas. Some consideration of Slight was given for the Big Country/Hill Country with a nearly stationary mid/upper trough upstream and copious moisture content present. Instability and convective coverage were in question though and will likely be dependent on prior-day convection and the evolution of any potential complexes from west Texas that migrate through the region during the early morning hours. After collab with local WFOs, decision was made to wait another model cycle before reconsideration of a potential upgrade. Though specific timing is uncertain, a disturbance over the central Gulf will begin to migrate slowly northwestward toward southeastern Louisiana and pose heavy rainfall potential across that area and adjacent areas of Mississippi. Wet soils from prior rainfall will support excessive runoff should heavier rainfall/deep convection materialize as suggested by models. Cook ...Previous Discussion... Upper Midwest... Additional scattered thunderstorm activity is expected once again ahead of a front making its way from Iowa into Wisconsin and vicinity, spreading 1-2 inches of rain with local amounts reaching 4 inches. Storms in that area should be progressive in nature due to 20-30 knot mid/upper level flow, though localized backbuilding and mergers may increase totals locally. The Marginal Risk surrounding the Slight Risk was largely unchanged...although some of the territory was removed from the northern part of Michigan now that timing of the boundary and low level moisture fields have become handled better by the models/ensembles. Texas into New Mexico... Weak mid/upper troughing across the southern Rockies and Texas will promote another round of thunderstorm activity across a large part of Texas and southern New Mexico, with attendant flash flooding expected due to slow storm motions and abundant moisture. Coastal Louisiana... A trough of low pressure interacting with the higher moisture in place will bring a higher coverage of thunderstorms with the potential for intense rain rates and localized heavy rainfall. Spaghetti plots show more ARW core members than NMMB...suggesting that there could still be shifts in placement or QPF amounts between now and the time the outlook verifies. Bann Day 3 Valid 12Z Sat Jun 06 2026 - 12Z Sun Jun 07 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE GREAT LAKES/OHIO VALLEY AND ACROSS THE MIDDLE GULF COAST INTO THE SOUTHERN PLAINS... ...21Z Outlook Update... The overall forecast is on track with minimal changes made based on latest model trends. The Slight Risk along the Upper Ohio Valley westward to Illinois was expanded/shifted southward and westward to account for latest model trends, which develop scattered thunderstorm activity (likely in the form of clusters/linear segments) across the discussion area during the afternoon and evening. Guidance has shifted somewhat more south with precip maxima into northern West Virginia, with more isolated thunderstorm activity expected with westward extent into Illinois. Isolated instances of flash flooding appear possible in this regime. Across Texas and Oklahoma, a persistent mid-level trough will likely continue to spawn scattered to numerous shower/thunderstorm activity, with latest guidance depicting QPF maxima near the Red River and into western north Texas. Much of this evolution will depend on development and persistence of any complexes from prior- day convection, which lends uncertainty at this timeframe. Should trends hold, a Slight may be needed in portions of west Texas and the Big Country. Lastly, models are in general agreement that a Gulf disturbance will reach land over southeastern Louisiana and spread areas of heavy rainfall over Louisiana and Mississippi. Local convective training/banding may be possible depending on the organization of the disturbance. Current trends suggest additional heavy rainfall potential over wet/sensitive ground conditions from prior rainfall in the area the past couple weeks. Flash flooding is possible on at least an isolated basis. See the previous discussion below for more information. Cook ...Previous Discussion... Great Lakes/Ohio Valley... Maintained a Marginal Risk area over portions of Ohio Valley and nearby southern Great Lakes as a front become oriented along an east to west axis and flow aloft is weakly forced to lift isentropically. Maximum areal average rainfall after the start of the period at 12Z Saturday generally looks to be little more than an inch. The cumulative effect of rainfall on Days 2 and 3 suggested it was too early to entirely remove the Marginal. Texas northward into the Southern Plains... Little change in the overall synoptic pattern is expected with southerly flow of moisture continuing to be drawn into parts of the Southern Plains. Some stronger/better defined shortwave energy within the flow aloft will promote yet another round of thunderstorm activity across a large part of Texas and southern New Mexico and extending as far north as parts of Oklahoma/Arkansas and Kansas by late Saturday night/early Sunday morning, with attendant flash flooding expected due to slow storm motions and abundant moisture. 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