FOUS30 KWBC 070048 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 848 PM EDT Mon Jul 6 2026 Day 1 Valid 01Z Tue Jul 07 2026 - 12Z Tue Jul 07 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID ATLANTIC AND SOUTHERN NEW ENGLAND... ...Mid Atlantic to Southern New England... PWAT anomalies maintain +2 to +3 deviations as we move through the evening across much of the Mid Atlantic and Northeast. Latest mesoanalysis indicates 2.0-2.4" PWAT relevant across much of VA/NC and points northeast along and east of I=95. Present pattern indicates the best instability, however, will reside over VA/NC up through the western half of PA with its orientation driven by the residence of a quasi-stationary front over the area. Scattered thunderstorms are already causing issues across western PA down into WV and VA given the environment in place with the threat likely to continue for several more hours before dissipation. The activity across central and southeastern VA will likely maintain a presence beyond 06z before finally dwindling, but even still some cells could linger well into the early morning hours Tuesday. Low FFG's across many areas in the Mid Atlantic precluded the activity in question, so the threat for flash flooding remains more elevated than normal. For more on the threat across western PA down into the Central Mid Atlantic, please see MPD #0632. For more information on the current threat into VA, see MPD #0630. Given the above, the SLGT risk over western PA down through the Central and Southern Mid Atlantic remains with a high- end SLGT forecast for that area of western PA between I-80 down to the M/D. For the Northeast, surface low will wander off the northern Mid Atlantic coast with some onshore component likely to materialize over parts of Southern New England. The issue in sustaining a more appreciable threat for flash flooding is the lack of general instability with the area theta_E pattern relatively benign for areas inland, away from the coastal plain. Increasing low-level convergence will transpire over Southern New England which could produce some low-topped convection capable of locally heavy rainfall given the antecedent environment. In this case, this was enough to maintain the SLGT risk over the above areas, but not enough of a risk to maintain the previous Moderate risk, so that was removed with coordination from the local WFO's. ...Upper Midwest... Energetic shortwave rolling through southern Canada extends into the northern tier of the CONUS with thunderstorms migrating southeast through the North Woods of MN. Expectation is for the convection to be heavy enough to potentially cause some isolated flash flood concerns, but likely too progressive to cause more significant problems. Will monitor the southwestern edge of the convective signature for possible training as indicated via a few of the CAMs this afternoon/evening, but for now, the MRGL risk was more than relevant for this setup. ...Texas into Tennessee Valley... A few disturbances will interact with a generally favorable environment in place to allow for an isolated flash flood threat from the central RGV all the way back into the Tennessee Valley. A few more organized complexes are moving through the Lower Mississippi Valley currently which will be the root of any flash flood concerns in that area for the next several hours. MRGL risk remains in these areas for the limited threat overnight. Kleebauer Day 2 Valid 12Z Tue Jul 07 2026 - 12Z Wed Jul 08 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE NORTHERN PLAINS AND MID-ATLANTIC... 20z Update: A Slight risk was added across portions of the Mid- Atlantic where cell mergers near a backdoor front should lead to isolated to scattered flash flooding. Pretty good agreement between the 12z HREF and REFS on this axis from portions of southwest PA into central VA and northeast NC, with rainfall expected to locally exceed 3". The Marginal risk was expanded across the TN Valley and into portions of the lower MS Valley. Convection along this corridor should be disorganized and pulse in nature...however lingering high moisture and instability will support heavy rainfall rates and a localized flash flood risk where cell mergers occur. The Slight risk across portions of the Dakotas into MN still looks in good shape, and so only minor adjustments were made. Chenard ...Previous Discussion... ...Northern Plains... During this period a shortwave rounding the ridge anchored over the Four Corners will make its way through central Montana to western Minnesota. This shortwave will drive downstream PVA and height falls while concurrent but modest RRQ diffluence in the tail of a distant jet streak helps enhance synoptic lift. At the surface, a wavering boundary with a wave of low pressure moving along it will try to shift north in response to subtly increasing southerly low- level flow, with the resulting isentropic ascent aiding lift across the region. This robust ascent will act upon PWs that will surge to 1.25 to 1.75 inches, or around +2 sigma, collocated with a plume of MUCAPE exceeding 2000 J/kg. Areal coverage of convection will increase through the day, tracking from west to east. The environment will be favorable for backbuilding or training. Hourly rainfall as much as 0.75"-1.0"+ is likely, which could create locally 2-3" of rainfall as reflected by modest (5-15% chance) of 3"/24 hrs. Soils across this part of the country have been recently wet thus increasing sensitivity. A Slight Risk remains in effect from the eastern Dakotas to western Wisconsin. A broad Marginal Risk extends from eastern Montana to north-central Wisconsin. ...Mid-Atlantic States... Much of this region will continue to have scattered to widespread thunderstorms as weak impulses traverse through the trough overhead. In general, these storms should be of the pulse variety and move E/NE on 15 kts of 0-6km mean wind. However, the impressive thermodynamics in place (PWs over 1.75 inches overlapping MUCAPE of 1000-2000 J/kg) will support rainfall rates of 1-2"/hr, through which any short-term training or repeating rounds could lead to instances of flash flooding. ...Eastern Massachusetts & Rhode Island... A wave of low pressure will be tracking south of Rhode Island during this period keeping some showers and thunderstorms in place across southern New England. Although new accumulations are expected to be modest hourly rates of 1+ inches/hr will be possible. A Marginal Risk area was maintained for this period. Weiss/Campbell Day 3 Valid 12Z Wed Jul 08 2026 - 12Z Thu Jul 09 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES... The Slight risk over the Upper Midwest still look pretty good, although we did nudge it a bit south with this update. Convection should be ongoing at 12z Wednesday moving from west to east across MN and WI. While this activity could be moving along and weakening during the morning, we should see renewed development along the front by afternoon from southeast MN into WI. Approaching shortwave energy and an upper level jet will help drive this uptick in activity, with PWs above the climatological 90th percentile and CAPE approaching 2000 J/kg supporting heavy rainfall rates. While a progressive squall line should eventually evolve, there will be an opportunity for some training and backbuilding during the development and initial upscale growth phase of convection. Rainfall totals of 1-2" should be most common, but localized swaths over 3" are probable and supported by the 12z RRFS. A Marginal risk was added across portions of the OH/TN Valley into the Mid-Atlantic. A shortwave moving across KY/TN and a lingering backdoor front over WV/VA should both act as a focus for convective development Wednesday. Not expecting anything too organized or widespread, but enough moisture and instability will be around to support locally heavy rainfall rates. Chenard Day 4 and Day 5 Valid 12Z Thu Jul 09 2026 - 12Z Sat Jul 11 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE OHIO VALLEY AND CENTRAL APPALACHIANS ON DAY 5... 20Z Update: Additional information provided on an upgrade for the D5 period with a maintenance of a broad MRGL for D4, below. Stronger flow will initially remain along the northern tier of the CONUS early to mid-week with mean upper-ridging across the western to central U.S. Embedded shortwaves rounding the upper-ridge will eventually lead to deepening troughing across the the Midwest and adjacent areas on Thursday. The southward shift of stronger flow aloft into the central Plains east through the Middle Mississippi/Ohio/Tennessee Valleys and Lower Great Lakes will bring more scattered thunderstorm chances across the region. Seasonably high instability and moisture pooling along a southward progressing, wavy cold front will support locally heavy rainfall bringing the threat for at least isolated instances of flash flooding, and a broad Marginal Risk of Excessive Rainfall exists for D4 (Thursday) with enough confidence to upgrade a large portion of the Ohio Valley and Central Appalachians to a SLGT risk for D5 (Friday) as increasing low-level convergence ample mid-level ascent will likely trigger widespread convection with training potential over the region, compounding with any impacts from convection the previous forecast period. Consensus grew over the past series of NWP updates with the ensemble mean QPF structure signaling a large area of 1-2" areal average totals with embedded higher amounts positioned over the southern-third of IL/IN/OH through much of KY into WV. This is coincident with the progression of both the front and a strengthening shortwave trough migrating out of the Central Plains into the region as we move into Friday. ML output is also favoring the Ohio River Basin into the Central Appalachians extended from southwestern PA down through WV as terrain influences along with the synoptic evolution will couple into a targeted threat for heavy rainfall and local maxima sufficient for scattered flash flood prospects. PQPF forecast for at least 1" signals a broad 20-40% probability with a bullseye of 50-80% located over the Central Appalachian front in northern WV. This is a relatively bullish signature at this lead, enough to warrant an upgrade to a SLGT risk over the aforementioned areas from IL to WV. Putnam/Kleebauer 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 $$