FOUS30 KWBC 290036 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 836 PM EDT Sun Jun 28 2026 Day 1 Valid 01Z Mon Jun 29 2026 - 12Z Mon Jun 29 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN AND NEAR EAST TENNESSEE, NORTH CAROLINA, AND PORTIONS OF NORTHWEST MONTANA... ...Montana... An upper low center pivots over Montana with the surface low wobbling near 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. Some refinement to the areal extent was made per radar reflectivity trends and 12z REFS/18z HREF mesoscale guidance signals. ...Northern Plains/Upper Midwest... The warm sector of this anomalous low over MT is having issues shifting eastward as the parent cyclone loops near the Alberta/ Saskatchewan/Montana border. Gulf moisture advects up the length of the Great Plains through the Upper Midwest. Convection is expected to flare up across portions of the Dakotas and WI/MI this evening into tonight. Any issues caused by the heavy rainfall appear to be isolated. The Marginal Risk area was split in two, based on radar reflectivity trends and 12z REFS/18z HREF mesoscale guidance signals. ...Coastal Carolinas/Mid-Atlantic... A Slight Risk was maintained over eastern North Carolina into far southeast Virginia for ongoing convection expected to move eastward over the next several hours. Coverage has been enough to result in some cell mergers and brief training enhancing rainfall rates/duration. Another Slight Risk area continues for areas in and near eastern TN as a precaution where the guidance still has some signal for heavy rainfall overnight. ...West Texas... A Marginal Risk was kept over west TX, where dryline convection should pose a localized flash flood risk this evening into tonight. Roth 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... 21Z update... In general, the area identified for having an elevated threat for excessive rainfall and isolated areas of flash flooding remain in good order. Small adjustments were made with the southern boundary across central Nebraska to reflect the latest WPC QPF and model trends. A modest southern expansion was made into eastern Idaho and northwest Wyoming to account for the precipitation occurring during the Day 1 period and a southern shift in QPF placement in the latest guidance. Campbell 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... 21Z update... Modest southward adjustments were made to the western bounds further into northern Nebraska and for the northern boundary in central Minnesota. This maintains a southwest to northeast orientated axis from the Plains to Michigan. Campbell 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... 21Z update... The environment described below is still expected although the guidance shifted the QPF footprint a bit east than previous cycles. As such, the Marginal Risk area was adjusted to cover more of the Florida Panhandle and reduce coverage over eastern Louisiana and souther Mississippi. Campbell 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 ...Northern Plains/Upper MS Valley/Upper Lakes... Not a lot of changes overall to the large scale flow pattern 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 for similar areas between portions of Nebraska/South Dakota and portions of Michigan. Roth/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 $$