475 FOUS30 KWBC 032226 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 626 PM EDT Fri Jul 3 2026 Day 1 Valid 2218Z Sat Jul 04 2026 - 12Z Sat Jul 04 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF IOWA AND EASTERN NEBRASKA INTO NORTHEAST KANSAS AND NORTHWEST MISSOURI... 22z Update: A quick update was made to some of the Marginal risk areas. First, we added a Marginal risk to cover MPD 578 over portions of the Mid-South. Cell mergers are resulting in a localized Urban flash flood risk here, but the threat should quickly wane with the loss of daytime heating. A Marginal risk was also added over portions of northern MN into northern WI and the U.P. of MI. Slow moving convection near a front could lead to an isolated flash flood through the evening hours. Also dragged the Marginal risk into more of the High Plains from KS into eastern MT to cover an isolated flash flood threat as convection develops this evening and moves eastward. Chenard ...Previous Discussion... ...Northern/Central Plains to the Midwest... 16Z Update: Heavy rainfall this morning way over-performed in areas centered over Central IA within proximity of a surface trough analyzed overhead. The setup across the Plains remains a bit complex with the passage of multiple shortwaves and the undulation of formidable theta_E/instability maxima being advected into the region on the lead of a broad trough to the west. Models continue to struggle in this setup which is customary with more weakly forced environments dominating the synoptic and mesoscale convective scheme. The trend the past several days has been for heavier precip to shift south of where guidance is suggesting, and this is likely trending in that direction just based on observational tendencies the past 24 hrs. This would also correlate well with the ML outputs remaining a solid 50-100 miles south in their depictions of where the heaviest precip is forecast (albeit still missing the mark on magnitude by a considerable margin). Considering the upstream shortwave propagation into Central High Plains today, carrying eastward through the period and beyond, the forecast is likely to be correct in cell initiation across central and eastern NE later this afternoon, however the thought process is the cold pool maturation generated by any convection will likely propagate further southeast with the target of heaviest rainfall likely to be centered across the Missouri River basin and surrounds encompassing southeastern NE down through southwestern IA, northwest MO, and northeast KS. This is actually addressed in a few of the CAMs, but still not a great consensus at the moment as models are struggling even at initialization this morning with ongoing convection. The SLGT risk was adjusted south to account for historical trends and expectation for cells to migrate further southeast after initiation later this evening. Heavy precipitation over Central IA at any point is liable to cause problems given the antecedent top layer soils fully saturated with flooding ongoing in some areas to the north of Des Moines where 5+ inches have fallen since the overnight time frame. Showers and storms will develop east from there through the Chicago metro and along Michigan's southern border through the day, but short residence times of the heavy rainfall due to sufficiently fast movement of the storms should keep any flash flooding risk in these areas isolated and consistent with a Marginal Risk. This pattern remains steadfast in guidance with persistence in the flow over the area as the western Lakes area remains far enough removed from the greater mid and upper forcing evolution over the Central High Plains. A MRGL risk was also expanded over more of southwestern SD due to a complex upper pattern that materialized over the area this morning. The current setup calls for training/back-building convection over the area near Rapid City for at least another 2-4 hours before activity can finally begin to vacate the area. More on this setup and the drivers of the local pattern can be reviewed in the latest MPD #0575 issued for the region. Kleebauer ...Southeast Florida... ..16Z Update: Little to no change to the previous MRGL risk placement as convection billowing up along the sea breeze with western cell motions could spur an isolated flash flood threat in any urbanized settings in southeast FL. HREF probs continue to depict modest 20-40% probabilities for local amounts greater than 5" with a higher confidence (60-80%) for greater than 3" over the same area. Highest confidence in more appreciable totals continues to be over central FL to the west of Lake Okeechobee, but those areas tend to be much harder to flood considering very high FFG's bordering 4-5" per hour necessary. Low probs for >3" per hour allowed a continued nil in that area, but a non-zero chance is forecast given the heavy rain anticipated. Will monitor for any adjustments necessary as activity occurs. Kleebauer ..Previous Discussion.. Afternoon convection expected to develop/increase across the middle of the state south of Lake Okeechobee, then slowly drifting east towards the urban corridor from West Palm Beach south, where any isolated flash flooding threat exists. A small Marginal Risk area was maintained. Putnam/Campbell Day 2 Valid 12Z Sat Jul 04 2026 - 12Z Sun Jul 05 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER SOUTHEAST KANSAS INTO NORTHEAST OKLAHOMA... ...Kansas into Oklahoma... 20Z Update: Increasing confidence in the generation of an MCS across the Central Plains, moving southeast into the Lower Mississippi Valley Saturday evening in conjunction with a cold front approach from the north and surface low positioned over the adjacent Southern Plains. Both hi-res and global deterministic have a signal for convective initiation after 00z Saturday over KS with upscale growth anticipated downstream of any cell clusters that materialize as they move into a budding LLJ. This is a fairly typical signal for such a synoptic pattern with increasing low- level convergence ahead of an approaching cold front. Low-level flow will become backed for a time across the area of southeast KS into northeastern OK ahead of the front according to forecast soundings from various deterministic CAMs. This leads to effective boundary layer shear approaching 35-40kts will be efficient in sustaining stronger updrafts and mesocyclone formations capable of strong to severe cells, even in the case of cell mergers. PWATs between 1.8-2.1" are expected in the area of interest allowing for a deep moist profiles suitable for heavy rain cores. HREF probs for >1"/hr rates are actually prolonged within the temporal aspect of the forecast over the region with a solid 30-50% prob from 00z-12z Saturday across the aforementioned area meaning some back-building behind any organized convective pattern is plausible. Modest 30-50% probs for >3" exist over the area from I-70 west of Kansas City down through Tulsa with the highest probs located over northeast OK. Isolated low-end probs for >5" also exist, but are generally noting the top-end of the potential for the threat as the progression of the MCS should limit the prospect for more appreciable impacts/coverage. Given the agreement within the guidance, and the threat for modest probs exceeding local FFG markers, a SLGT risk was added across the area extending from west of Kansas City in eastern KS, down into northeast OK and clipping the counties in AR/MO along the neighboring state lines of KS/OK. ...Midwest into the Mid Atlantic... 20Z Update: Widespread thunderstorm development is anticipated over the eastern half of the CONUS as we move through Saturday afternoon and evening with pulse convection most likely for a majority of the region with perhaps more organized cell clusters over the Upper Midwest into the Great Lakes thanks to shortwave progressions over the area. Vorticity maxima will slide eastward over the top of the broad ridge drifting eastward off the Atlantic coast leading to more return flow and lower prospects of mid-level subsidence capping the threat of convection. HREF probs for >2" show a "popcorn-like" output in various little maxima all over the eastern CONUS from the Mid Atlantic into the Ohio Valley with more maxima showing up across the Upper Midwest and northern MI. Any thunderstorm will be capable of producing local rates of 1-2"/hr which could result in isolated cases of flash flooding over a broad area with the focus likely within any urban corridors or complex terrain (Appalachia). A broad MRGL risk exists over the above regions to account for the threat. Kleebauer Day 3 Valid 12Z Sun Jul 05 2026 - 12Z Mon Jul 06 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID-ATLANTIC... 20Z Update: The SLGT risk inherited was maintained with some expansion into southwest PA and bordering areas of northern WV in conjunction with trends in higher QPF over the area from scattered thunderstorms developing with the approach of the cold front. This area historically is more prone to flash flooding due to terrain influences and more sensitive hydrologic schemes, so the signal offered enough support to expand the risk westward to account for the potential. Otherwise, scattered flash flood concerns exist over the Central Mid Atlantic with an increasing risk of heavy convection over portions of PA down through the DC-Balt-Phi corridor. Kleebauer ..Previous Discussion.. The pattern setting up during this period is favorable for heavy rainfall, especially near the Appalachians and locations east toward the Eastern Shore. A low to mid level trough interacting with a backdoor front should provide a focus for heavy rainfall and at least moderate levels of instability should overlap with PWs over 2" across portions of the region. There will also be the potential for training and backbuilding of convection as westerly flow aligns with the boundary. A Slight Risk area covers most of Pennsylvania, Maryland, northern Virginia, and portions of Delaware and New Jersey. A broad Marginal Risk area spans from eastern Oklahoma eastward to the Mid-Atlantic/southern portions of the Northeast. Campbell Day 4 and Day 5 Valid 12Z Mon Jul 06 2026 - 12Z Wed Jul 08 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID-ATLANTIC ON MONDAY... A Slight risk remains over portions of the Mid-Atlantic on Monday, focused near a stationary front. Near and just south of this front instability of 2000 J/kg or greater and PWs over 2" are forecast, an environment supporting efficient rainfall and high hourly rates. The Slight risk area was aligned along the southern half of the multi-model max QPF consensus, which is where the optimal overlap of instability and moisture should exist. Additionally, since some of this region is expected to receive locally heavy rainfall on Saturday and/or Sunday, antecedent soil conditions by Monday could be more saturated, possibly resulting in lowered FFG and increased hydrologic sensitivity. Further north of the Slight risk, stronger low level convergence will be capable of producing a broader area of moderate to locally heavy rainfall across NY into southern New England. However, a northward drop off in instability is expected to limit peak rainfall rates, warranting only a Marginal risk for these areas at this time. Some latitudinal uncertainty continues with regards to the axis of greatest flash flood potential, and so some adjustment to the Slight risk is likely over the coming days. While a localized flash flood risk could linger into Tuesday (day 5), forecast confidence drops off enough by that time to preclude introducing any risk areas at this time. A new Marginal risk was introduced across portions of the Northern Plains for Tuesday. Model consensus is suggesting an organized convective potential driven by a progressive shortwave rounding the top of the upper level ridge. This forcing, combined with increasing low level moisture transport, should lead to convective clusters capable of producing localized swaths of heavy rainfall. Chenard 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 $$