FOUS30 KWBC 281602 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1202 PM EDT Sun Jun 28 2026 Day 1 Valid 16Z Sun Jun 28 2026 - 12Z Mon Jun 29 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR CENTRAL/SOUTHERN KENTUCKY INTO NORTHEAST TENNESSEE, EASTERN CAROLINAS, SOUTHWEST Pennsylvania INTO NORTHERN WEST VIRGINIA AND Virginia, FOR FOR PORTIONS OF NORTHWEST MONTANA... 16Z update... The Moderate Risk was downgraded to a Slight across the Ohio/Tennessee Valleys as convection was rapidly decreasing as drier air began cutting off the moisture stream. With the ridge building in from the west, redevelopment will be minimal or nonexistent therefore the Marginal and Slight Risk areas were greatly reduced across the region as well. However there is a growing signal for localized heavy rainfall across parts of the Appalachians and surrounding areas. The Marginal Risk was expanded northward in Pennsylvania and a targeted Slight Risk was raised to cover northern portions of the Virginia, West Virgina and southwest Pennsylvania. Out West, a Slight Risk was raised for portions of northwest Montana as above average PW values are fueling the rainfall wrapping around the Canadian low and moving southward into Montana and Idaho. There could be hourly rates in the 0.30 to 0.70 inches/hr at times which does elevate the threat for localized flash flooding especially in the areas of steep terrain. The Marginal Risk area was also expanded south/southwest into Idaho as well. Campbell ...Ohio/Tennessee Valley... The latest satellite and radar trends show an increasingly organized band of heavy showers and thunderstorms becoming focused across areas of southwest IN down through central and southern KY and into northeast TN. Cooling cloud tops are noted especially over southern KY, and the environment is very moist and moderately unstable with MLCAPE values of 1000 to 1500 J/kg and PWs locally as high as 2.0 to 2.25 inches. Favorable Corfidi vectors and low- level westerly flow/warm air advection should favor a continuation of heavy showers and thunderstorms that will be capable of extreme rainfall rates. Some of these rates may reach 2 to 3 inches/hour though the morning hours, with some additional totals of 3 to 5+ inches possible. The multi-model consensus strongly suggests the ongoing convection should weaken toward midday or early this afternoon, but at least in the near-term, the additional rainfall and very sensitive antecedent conditions will favor additional concerns for flash flooding. Some of this flash flooding may be significant and life-threatening at least through the midday time frame. As a result, WPC has introduced an extension of the prevailing Moderate Risk which will include a northwest/southeast axis from far southwest IN down through central/southern KY and northeast TN. ...Montana... Upper low center pivots over Montana Sunday with the surface low stalling along the international border . This maintains comma head/deformation zone rain shifting into northwest Montana where terrain enhances rates at lower elevations and snow generally at or above 6500 feet. This is more of an areal flood concern given a lack of instability, but localized rates may warrant some rapid flooding concerns where precip bands are most stagnant. 00Z consensus rainfall remained in the 1 to 3 inch range. ...Upper Midwest... The warm sector of this anomalous low over MT will continue to shift eastward allowing an airmass with robust Gulf moisture advection up the length of the Great Plains through the Upper Midwest. Organized showers and thunderstorms are expected to keep tracking eastward across parts of Minnesota...Wisconsin and northern Iowa with locally heavy rainfall rates given the magnitude of the moisture transport ahead of a surface cold front. ...Coastal Carolinas/Mid-Atlantic... A Slight Risk was maintained over eastern North Carolina into far southeast Virginia as an MCV currently over the southern Ohio Valley will be moving across North Carolina today.A convective focus ahead of this feature should occur across the aforementioned Slight risk area. Guidance indicates a mainly progressive convective mode, however coverage should be enough to result in some cell mergers and brief training enhancing rainfall rates/duration. Both the 00Z HREF and REFS indicate a 15-40% chance of Flash Flood Guidance exceedance although they struggled to capture the system moving across the Appalachians overnight leading into the start of the Day 1 period. For that reason...the Slight Risk area was expanded into more inland areas while a Slight risk over the Appalachians was introduced based on short term radar imagery showing multiple cells aligned to train over some areas that were doused on Saturday night. The Marginal Risk farther north was largely left as is given the signal for widely scattered to scattered convection that could be slower moving within a favorable environment for heavy rainfall rates. ...West Texas... A Marginal Risk was kept over west TX, where dryline convection should pose a localized flash flood risk. Orrison/Bann Day 2 Valid 12Z Mon Jun 29 2026 - 12Z Tue Jun 30 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM MONTANA INTO THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY, AS WELL AS ACROSS WEST TEXAS... ...Montana into the Northern Plains and Upper Mississippi Valley... Saw little reason to make major changes in this region. On-going convection at the start of the outlook period on Monday morning will be occurring in a highly unstable airmass with very strong low level moisture transport. 00Z model runs did little to settle the latitudinal of the convective axis and mode/movement. Given the impressive CAPE, very strong moisture transport, high PWs and weak Corfidi vectors...there is the potential for backbuilding convection and a locally significant flash flood risk. However, it's also a possibility that the strong mean flow and somewhat progressive forcing help move storms along and limit the coverage/magnitude of the flash flood risk. So we will just continue to continue to monitor trends over the coming days. While mostly stratiform rain by this time, event total rainfall of 2-4" is expected across portions of central and western Montana. Even though rainfall rates by this time should be low enough to preclude much of a flash flood risk, this is an impressive amount of rain for late June over this area, and thus some areal/stream flood impacts appear probable. Thus we will include them within the Marginal risk. ...Southwest Texas... Increasing instability should lead to late day convective development along and near the dry line in west Texas. Isolated flash flooding is again possible Bann Day 3 Valid 12Z Tue Jun 30 2026 - 12Z Wed Jul 01 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE GREAT LAKES...NORTHERN NEW ENGLAND AND OVER SOUTHWEST TEXAS... ...Northern New York State into Northern New England... Shortwave energy riding up over the top of an Ohio Valley upper high across southeast Canada will make its way into portions of northern New England on Tuesday and help strengthen the low level westerly flow into a frontal boundary. Models still point to the potential for organized convection late Tuesday or in the early morning hours of Wednesday. There remained a strong enough model signal for organized convection moving northwest to southeast resulting in heavy rains and isolated runoff issues, enough for a Marginal Risk, but not cohesive enough amongst the guidance for a stronger risk level. ...Southern High Plains... Precipitable water values of 1 to 1.5+ standard deviations above climatology for this time of year remain over the Southern High Plains. Embedded shortwaves in this southwest mid to upper level flow will support increasingly scattered convection in this anomalously moist airmass, with locally heavy rains and isolated runoff issues possible causing problems in burn scars and dry washes/arroyos. ...Upper MS Valley/Upper Lakes... Convection expected to continue along and ahead of a surface front moving slowly across the Upper MS Valley. Favorable right entrance region jet dynamics ahead of this front in an axis of above average precipitable water values will support potential for heavy rains with organized convection along and ahead of this cold front with isolated runoff issues possible. This outlook largely maintained the adjustments made previously...although additional southerly shifts cannot be ruled out given the flow pattern expected. ...Central Gulf Coast... Some of the guidance has a signal for heavy rainfall across the area, caused by an easterly wave coming off the tail end of a frontal boundary. Considering the moisture and instability expected, at least urban areas could receive flash flooding so maintained a Marginal Risk for this possibility. Bann Day 4 and Day 5 Valid 12Z Wed Jul 01 2026 - 12Z Fri Jul 03 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL THE UPPER MISSISSIPPI VALLEY/UPPER LAKES REGION ...Upper MS Valley/Upper Lakes... Not a lot of changes overall to the large scale flow pattern across the CONUS during the day 4 & 5 period. The closed upper high will remain in place across the East, with west southwest mid to upper level flow on its northwest side and to the east of the mean trof across the west. Shortwave energy moving northeastward in this west southwest mid to upper level will support active convection in an axis of slightly above average PW values across the Upper MS Valley/Upper Lakes region. Favorable right entrance region jet dynamics will also be present in this above average PW axis, supporting the potential for organize convection, heavy rains and isolated runoff issues each day across this area. A marginal risk was depicted both day 4 and 5 from eastern SD/far northeast NE, across northern IA, southern to central MN, much of WI into the U.P. of MI. Oravec 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 $$