FOUS30 KWBC 092006 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 406 PM EDT Tue Jun 9 2026 Day 1 Valid 16Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHERN PLAINS, OHIO AND TENNESSEE VALLEYS, AND SOUTHERN APPALACHIANS... .Northern Plains... 16Z Update: The trends in guidance maintain a signal for locally heavy rainfall over portions of North Dakota into northern MN later this evening. Progressive nature of the convection may limit the expanse of significant flash flood potential, however anomalous deep moist environment coupled with the energetic nature of the disturbance and a very buoyant environment will likely enhance convective cores, providing capability for rates to exceed 2"/hr in the strongest cells. CAMs have been generous with local amounts between 3-5" in the areas hardest hit with the bullseye focused over northeastern ND, so it's very plausible to see at least a few flash flood warnings arise in this setup. The previous SLGT risk was general maintained with some trimming of the southwestern flank to account for trends in the 12z CAMs indicating a local min just to the northeast of Bismarck. Kleebauer ..Previous Discussion.. A potent upper level trough will push across the northern Rockies into the Plains today and spur cyclogenesis over the northern Plains. Low pressure will strengthen over the region with a cold front extending to the southwest and a warm front extending to the east. Southerly winds ahead of the trough will direct warm, moist, unstable air into the northern Plains, with PWAT values expected to exceed 1.5 inches and MUCAPE expected to rise above 3000 J/kg. Increasing mid/low level winds on the leading edge of the trough will create a highly sheared environment that is conducive for supercell development this afternoon. By this evening, an intensifying low level jet oriented parallel to the surface cold front will support upscale convective growth into a linear MCS. Deep convection within supercells and eventually the more organized MCS will be able to tap into the atmospheric moisture to produce very intense rainfall rates in excess of 2 inches per hour. Relatively fast storm motion will be a limiting factor to the flash flood risk, but rainfall rates will be enough to overwhelm FFGs and cause flash flooding, especially if heavy rain occurs in urban environments. A Slight Risk of excessive rainfall remains in effect for the heaviest convective activity expected over central and eastern North Dakota and northwestern Minnesota. A broader Marginal Risk area extends into the Midwest where convection may focus along a surface boundary extending from the northern Plains cyclone tonight. .Ohio and Tennessee Valleys and Southern Appalachians... 16Z Update: First of two shortwaves are currently impacting the southern Ohio Valley this morning with the most notable zone of impact focused between the Ohio River basin near and west of Louisville into west-central KY between the I-65/75 corridors. 12z HREF was very aggressive in a signature of a pronounced 1-2 punch during the period with neighborhood probabilities for >3" showing a broad axis of 80+% across much of western KY and even some moderate probs for >5" (40-60%) located near and along the I-65 corridor. Very buoyant environment will be situated over the region for the entirety of the forecast with SBCAPE indices between 2000-3000 J/kg likely to encompass the area of interest. Heavy precip chances will expand away from the above areas, as well, with the prospects for rainfall rates between 1-3"/hr expanding north and northwest across southern IN/IL, as far south as north-central TN, and as far east as southern WV as enhanced theta_E advection on the western and northern flank of the ridge over the Southeast will control the overall pattern and subsequent mean flow of any activity that materializes. The SLGT risk remains over a broad area of the southern Ohio Valley and neighboring Tennessee Valley with a high- end SLGT threshold pin-pointed across the western two-thirds of KY with emphasis on that zone between the I-65 and I-75 corridors down to the TN state line. Other area of interest in the period will lie across eastern GA up through the SC and western NC Piedmont where persistent south to southeasterly flow around the ridge will maintain a narrow tongue of elevated instability and deep moist advection that has maintained a round of heavy convection this morning. This threat will last for another 2-4 hours before dissipating, but maintained the SLGT to account for what is already occurring. Kleebauer ..Previous Discussion.. An upper level trough will lift northeast across the Midwest and Great Lakes region today accompanied by a surface low over the Great Lakes and a slow-moving warm front extending south into the Ohio and Tennessee Valleys. The air mass in place across these regions will be anomalously moist with PWAT values around 2 inches, 2-2.5 standard deviations above normal for this time of year. There will also be sufficient synoptic forcing and instability to support scattered to potentially widespread convection from the Great Lakes to the Interior Southeast. Convection will be ongoing at the start of the period and should translate east throughout the day as the system progresses. High moisture content in the atmosphere will support chances for locally heavy rainfall, and more intense rainfall may be possible over the Ohio and Tennessee Valleys where convection will be enhanced by a couple quick-moving mid-level waves rounding the top of the ridge positioned over the Gulf. The first wave will pass over the region early in the period, resulting in a burst of more intense convection this morning. The second wave will pass over this area tonight into early Wednesday morning and will have the potential for back-building storms along a surface boundary extending into the lower Ohio Valley from the northern Plains cyclone. Hi-res guidance suggests rainfall rates of 2-3 inches will be possible in stronger cells, and most hi-res CAMs are showing a swath of rainfall totals of 3-5 inches, with locally higher amounts, across portions of Kentucky and maybe southern Indiana as well. The HREF and RRFS are both showing relatively high probabilities (50-70% and 40-50% respectively) of 24 hr totals exceeding 5 inches in this area. Enhanced convection will also be possible, but to a lesser extent, under the upper waves over Tennessee and in upslope areas of the southern Appalachians. Some areas may be more susceptible to heavy rain today after recent heavy rains over the past few days. A Slight Risk of excessive rainfall covers the area of enhanced convection over the Ohio and Tennessee Valleys and southern Appalachians and a Marginal Risk area extends north through the Great Lakes. Dolan Day 2 Valid 12Z Wed Jun 10 2026 - 12Z Thu Jun 11 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE CENTRAL PLAINS UP THROUGH THE MIDWEST... .Midwest and Central Plains... 20Z Update: A larger change was implemented for the D2 period, but much of the synoptic scale evolution described in the previous forecast was maintained. 12z CAMs were finally able to depict the full D2 window with a broader scope of heavy rainfall potential within the budding warm sector across the Midwest. Strengthening theta_E ridge across the Central U.S. east of I-35 will be one of the more important aspects of the forecast as the meridional push of unstable air ahead of the maturing front will aid in a moderately buoyant environment with increasing large scale ascent aligned from southwest to northeast from KS up through WI. Shear levels will be highest further north into IA/IL/WI leading to more organized cell clusters propagating east/southeast through the region. Models are struggling with specific convective placements, so we have a few camps on positioning of the heavier rainfall for the period. Recent ML output aligns the heaviest precip over southeast NE up through the Mississippi River Valley between IA/IL with a northern expanse into WI. HREF neighborhood prob fields for >2" is highest across north-central WI between Eau Claire to Green Bay with several other "bullseyes" situated between northern MO through eastern IA, northern IL, and southern WI. Rates between 2-3"/hr are forecast in the strongest cell cores with the highest rates correlated over the area where CAPE can breach 3000 J/kg. This leads to a southern tail in heavier precip potential arcing back towards southeast NE to eastern KS where greatest instability is forecast. Considering the more widespread modest neighborhood probs and expected environment across a very large area ahead of the maturing synoptic pattern, a SLGT risk was expanded northeast to include much of the Midwest situated east of the Mississippi River, tailing back through portions of IA/NE/KS/MO. Kleebauer ..Previous Discussion.. On Wednesday, the northern Plains cyclone will move into south- central Canada and push a trailing cold front across the Midwest. Showers and storms will be ongoing Wednesday morning ahead of the system over northern Minnesota, then another round of convection is expected across the Midwest and Central Plains Wednesday afternoon and evening ahead of and along the cold front. Deep southerly flow ahead of the system will increase PWAT values to 1.5-2 inches, with the higher values focused between northern Missouri and southern Wisconsin. Instability should increase through the afternoon as daytime heating kicks in, but the best instability (3000-4000 J/kg) looks like it will focus from eastern Kansas and southeastern Nebraska into northern Missouri and southern Iowa, where there is a Slight Risk of excessive rainfall. This area will likely experience a period of enhanced convection Wednesday night as a frontal wave develops at the intersection of the cold front and a dryline. A secondary wave of moisture and instability will surge into the central Plains as a low level jet strengthens Wednesday night, which should support efficient rainfall rates, potentially exceeding 2 inches per hour, that could lead to scattered instances of flash flooding. Dolan .Tennessee Valley and Southern Appalachians... 20Z Update: Only minor changes were necessary across the Tennessee Valley to Southern Appalachian front with the changes more reflected in the change in CAMs QPF output and positioning of convection on Wednesday morning. The MRGL risk remains with best potential over eastern KY/TN over into southwest VA and down through the western Carolina's. Kleebauer ..Previous Discussion.. Convection should be ongoing across portions of the Tennessee Valley and southern Appalachians at the start of the period. A quick-moving upper level wave will round the top of the ridge positioned over the Gulf and support a period of enhanced convection late Tuesday night into Wednesday morning. Anomalous moisture and sufficient instability will be in place to support efficient rainfall rates, and slow storm motions will contribute to high rainfall totals. There will also be some potential for back- building storms along a surface boundary extending from the northern Plains/southern Canada cyclone into the Tennessee Valley, mainly focusing over Kentucky. Showers and storms will also be enhanced by upslope flow along the southern Appalachians. Convection should start to weaken Wednesday morning and wane by Wednesday afternoon, but there will at least be enough rainfall over saturated soils to continue a Marginal Risk of excessive rainfall into Wednesday morning. Dolan .Northeast U.S... 20Z Update: The MRGL risk remains for portions of the Northeastern U.S. with the primary area of interest likely across Upstate NY down through eastern PA. The main change was an expansion of the risk down through much of eastern PA, northwest of the metro corridors as recent CAMs have been highlighting a secondary area of focus within an expected developing surface trough bisecting the central Mid Atlantic up towards the Pocono's. Increased convergence signature within a maturing instability axis across the Mid Atlantic will lead to a period of heavy rainfall prospects within the confines of the boundary as it evolves during the afternoon Wednesday. 12z HREF probs are quite bullish over the Lower Susquehanna Valley between US15 to US422 in PA with modest probs for >3" locally in that region of southeastern PA. This area was highlighted in various CAMs which typically is a signal for at least a low-end threat given the overlap. Will be something to monitor over the next 24 hours for the potential. Kleebauer ..Previous Discussion.. A Marginal Risk of excessive rainfall was introduced for portions of the Interior Northeast. An upper level trough will cross over the Great Lakes into southeastern Canada accompanied by a surface low pressure system that will bring precipitation chances to much of the Northeast. The warm sector of this system will be characterized by an anomalously moist air mass with PWAT values up to 2 inches. There should be enough moisture and synoptic forcing to support locally heavy rainfall in stronger convection near the low pressure center over southeastern Canada and the Interior Northeast. Rainfall totals and flash flood potential may also be increased by terrain and upslope flow Wednesday afternoon. Dolan .Southwest Florida... Sea breeze pattern with convergent winds around the southern periphery of high pressure to the north will create a period of heavy convective potential across southwest FL by Wednesday afternoon. HREF probs for >3" along the coast between Port Charlotte to Naples are between 60-90%, but do fall back to lower probs between 15-30% for the >5" threshold meaning forecasts consistently show a range between 3-5" in the hardest hit locations. Area FFG's remain high, however the urban zones along I-75 will be the most susceptible to localized flash flood chances. This setup is likely to materialize between 18z Wed and 02z Thu before dissipating. A MRGL risk was added to the aforementioned area to cover for the low-end threat. Kleebauer Day 3 Valid 12Z Thu Jun 11 2026 - 12Z Fri Jun 12 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHEASTERN MISSOURI THROUGH EASTERN IOWA AND NORTHERN ILLINOIS TO SOUTHERN WISCONSIN... 20Z Update: Little change was necessary for the D3 time frame as the multi-model consensus continued to depict quite the widespread heavy rain prospect over the Midwest. The scenario is a classic frontal ascent pattern capable of a swath of heavy rainfall over several states as the front marches eastward. Highly anomalous PWATs and large scale low to mid-level ascent will be the primary drivers for the setup, favoring areas from northern MO up through the Central Midwest, including the metro areas like the Quad Cities, Chicago, and Milwaukee. Widespread 1-3" of rainfall with isolated totals upwards of 5" will be plausible in the setup, so the previous SLGT risk was sufficient for the period. Kleebauer ..Previous Discussion.. The frontal wave that developed over the central Plains Wednesday night will progress northeast and intensify as a strong upper trough swings into the northern and central Plains Thursday morning. A strong low level jet will increase moisture and instability across the central Plains Wednesday night, and this air mass will expand towards the Upper Midwest as southerly winds surge ahead of the surface frontal boundary. A large swath of high PWAT values above 2 inches will stretch from the southern Plains to the Midwest, which will support a broad area of convection capable of producing locally heavy rainfall. A wave of deeper convection will accompany the strong frontal wave as it progresses, resulting in high rainfall totals over an area from northeastern Missouri through eastern Iowa, northern Illinois, and southern Wisconsin. These areas are highlighted by a Slight Risk of excessive rainfall to account for enhanced convection capable of producing scattered instances of flash flooding. A broader Marginal Risk of excessive rainfall surrounds the Slight and includes much of the Midwest and portions of the central and southern Plains. Dolan Day 4 and Day 5 Valid 12Z Fri Jun 12 2026 - 12Z Sun Jun 14 2026 ...THERE IS A DAY 4 MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE SOUTHERN PLAINS TO THE NORTHERN MID-ATLANTIC... Widespread showers and thunderstorms will develop along and out ahead of a strong and expansive cold front that races into the eastern U.S. and becomes quasi-stationary over the South on Friday. PWs are likely to surpass the 90th climatological percentile ahead of the cold front from the TN and OH Valleys into the Northeast. Storms will be progressive and help to limit the footprint of potential flash flooding from the OH Valley on north into the northern Mid-Atlantic. However, the 00Z ECMWF-EFI does depict a minor signal (0.6-0.7) for unusually high CAPE-Shear for early- to-mid June over the OH Valley and Northeast. This environment is likely to support organized thunderstorms that contain heavy downpours and may cause localized flash flooding. Farther south, PWs will more commonly remain over 1.5" and in some instances approach 2.0" from the ArkLaTex to the Lower MS Valley. Storms could contain Excessive Rainfall rates as far west as the Guadalupe and Sacramento Mountains where SErly flow ushers in much above normal PWs. Burn scars in New Mexico could be at risk for flash flooding as a result. Mullinax ...THERE IS A DAY 5 SLIGHT RISK OF EXCESSIVE RAINFALL IN THE SOUTH CENTRAL U.S.... 850mb high pressure located over the eastern Gulf will work in tandem with lower pressure to the north and west to produce a deep fetch of rich moisture originating from the Bay of Campeche. The ECMWF ENS and NAEFS show IVTs >500 kg/m/s in the western Gulf aimed at south Texas, which is serving as the firehose that is introducing the anomalous moisture into the South Central U.S.. PWs above the 90th climatological percentile will be common from southern New Mexico and West Texas on east across the Southern Plains and into the Ozarks. At the same time, a cold front diving south from the Central Plains will collide with the hot/humid air- mass in the south to trigger numerous showers and thunderstorms. Storms are likely to persist into the overnight hours not just due to the persistent low-level jet, but due to the Central Plains and Ozarks ideal location beneath the diffluent right-entrance region of a 250mb jet streak. The 00Z ECMWF EFI does show a 0.6-0.8 area (indicating the potential for unusually heavy rainfall for this time of year) within the 00Z Sun - 00Z Mon time frame from eastern OK and southeast KS on east into the Ozarks, starting as early as Saturday night. After a couple days worth of rainfall across the region, there is added concern that soils will be more sensitive to Excessive Rainfall rates on Saturday. Where exactly the heaviest rainfall occurs will be determined upon the position of the frontal boundary located over the Central Plains. For these reasons, the Slight Risk remains in place for this forecast update. The localized flash flood threat is possible as far east as the Middle MS River Valley and as far west as eastern NM and western TX. Mullinax 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 $$