FOUS30 KWBC 040059 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 859 PM EDT Fri Jul 3 2026 Day 1 Valid 01Z Sat Jul 04 2026 - 12Z Sat Jul 04 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL STRETCHING FROM NORTHERN KANSAS INTO NORTHERN ILLINOIS... A broad Slight risk will continue into the overnight hours from northern KS into northern IL. A couple of ongoing convective complexes will result in an isolated to scattered flash flood risk over the next few hours. One over northern KS into Southeast NE is training along a convergence axis. The other across eastern IA into northern IL is progressing a bit more, but still seeing enough cell merging to pose a flash flood risk...especially over areas already hit with heavy rain earlier in the day. Overnight convection over the High Plains should persist and possibly grow upscale as it moves eastward across NE and KS. This activity may eventually move into the region currently seeing training convection over northern KS and Southeast NE, which would continue the flash flood threat over those areas. Overall, an isolated to scattered flash flood risk exists within the entirety of the broad Slight risk, with convection ongoing and additional development overnight. A Marginal risk extends eastward into OH and PA where convection tonight could briefly train resulting in an isolated flash flood risk. Convection over western SD and eastern MT is beginning to move, so the flash flood risk may be decreasing here, but localized instances of flash flooding are still possible as the activity moves eastward. Chenard 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 $$