561 FOUS30 KWBC 220945 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 545 AM EDT Mon Jun 22 2026 Day 1 Valid 12Z Mon Jun 22 2026 - 12Z Tue Jun 23 2026 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FROM NORTHERN ARKANSAS TO WESTERN TENNESSEE AND FAR NORTHWEST MISSISSIPPI... 0930Z Update... A Moderate Risk was added for northern AR to western TN and far northwest MS after assessing radar trends and latest HRRR/RRFS guidance. A mature MSC moving across eastern OK has an eastward extending wing of nearly stationary thunderstorms along an outflow boundary across northern AR into western TN and well south of the synoptic cold front to the north. The southward push of this outflow boundary is expected to compete with increasing southerly flow ahead of the MCS and strong mesovortex located in northeast OK. This all leads to an expected axis of heavy rain (hourly rates up to 3" and totals up to 6" are possible) through northern AR and into parts of western TN and northwest MS. This is just north of Little Rock, AR, but does include Jonesboro, AR and Memphis, TN. Coverage of flash flooding as well as potentially localized significant impacts prompted the upgrade to a Moderate Risk prior to the start of this day 1 forecast period (12Z Monday). This event is expected to begin diminishing by around 17Z as the MCS clears the region and weakens, but this still provides potential for around 6-hrs of intense rainfall rates and flash flood impacts. Snell Previous Discussion... ...Southern Plains to Tennessee Valley... Current WV satellite and UA analysis depicts a potent mid-level shortwave sliding southeast through the Central and Southern High Plains with eyes likely downstream into the Lower Mississippi Valley and southwestern Tennessee Valley as we move through the morning and afternoon Monday. Favorable boundary layer instability presence across much of the Southern Plains into the Southeastern CONUS will benefit periods of heavy rainfall during the period with a likely impact beginning early in the forecast period with a secondary batch likely to ensue the following evening. At the surface, surface wave will be located across OK in conjunction with an organized area of thunderstorms migrating southeast through the region overnight. A bit further east into the Ozarks and eastern OK, a slow-moving cold front will shift through the region overnight with increasing convergence likely to occur between the complex/surface wave and the front as it heads into central OK. Instability maximum over eastern OK into AR on the order of 2000-3000 J/kg MUCAPE will aid in the necessary component to initiate more thunderstorm activity as the convergence regime materializes with likely a long stretch of heavy convection orienting from south-central OK back into southwest TN by sunrise. PWAT anomalies between +1 to +2 deviations off the latest NAEFS indicate a deep moist convective environment situated over the area ahead of the front with the combination of both favorable instability and 2+ inch PWATs set to provide effective warm rain processes capable of producing efficient heavy rainfall that can spur flash flood capabilities. Recent 00z HREF outputs are pretty aggressive with scattered areas of 2-3" of precipitation anticipated in the means across the ArkLaTex through central and southern AR into southwest TN and western MS. A good portion of this rainfall is likely to occur in the first half of the period as the expected QLCS development will encroach the area and provide significant rainfall over the above locations. The disturbance over OK is forecast to utilize the positioning of the front as a focal point for the wave as model guidance agrees on the surface wave riding eastward along the front as it begins to enter eastern OK, eventually making headway into the Lower Tennessee Valley and MS Delta. Indications are for a small corridor between northeast AR through southwest TN into the Mississippi Delta to see a training episode materialize in the morning with neighborhood probs for >3" highlighting that zone with 50-70% probabilities. Some of the deterministic is very bullish within this general area noting totals of 4-6" in an isolated coverage with 2-4" more representative of an areal average. This expands back into central and southern AR as the complex of organized thunderstorms will likely slide south through Little Rock and surrounding areas creating a busy morning for flash flood prospects. This will likely expand into OK as the front location will be the main factor on where heavy precipitation would occur. In this case, the entire area is within a broad SLGT risk with a higher-end SLGT forecast across the above area between eastern OK into southwest TN and northern MS. As the complex of thunderstorms begins to peter off in the afternoon, another round of convection will spawn in-of the ArkLaTex into the eastern Red River area between OK/TX the following evening as a nocturnal LLJ develops after 23z with increasing convergence along the back edge of the front located in the area. There's still some discrepancy on the exact placement of the front, however there's enough consensus on the second round of convection to warrant attention to the prospects of flash flood potential into that area of the ArkLaTex to perhaps as far west as the I-35 corridor in southern OK towards the DFW metro. As of now, thunderstorm development is likely with training potential increasingly favored in the area as storm development will likely anchor to the front as mid-level flow aligns parallel to the boundary with surface convergence maximized along the front. A slow-moving axis of thunderstorms is a more textbook way for greater flash flood potential, especially in speaking in spatial terms as there will likely be a large area encompassed within this second round of convective development over that referenced corridor. If this were to make headway into I-20, this would likely result in numerous flash floods given the environment in place with rates between 2-3"/hr at peak intensity likely to occur. As of now, placed the region within the broad high-end SLGT forecast, but will have to monitor the CAMs closely over the course of the D1 to see if a targeted upgrade may be necessary for this band of heavy rainfall potential. ...Central Appalachians to Northeast U.S... Surface low currently analyzed over the western Ohio Valley will gradually lift to the east-northeast with an expectation for the low center to exit off the northern Mid Atlantic coast, dragging a cold front through the Mid Atlantic and Ohio Valley and lifting a warm front ahead of the disturbance. The current indications are for convection to spawn over the eastern Ohio Valley by the early- afternoon as mid-level ascent and increased surface forcing aided by the cold front and area of low pressure will trigger convective initiation just upstream of the terrain in WV and western PA. This area of thunderstorms will migrate eastward, entering a favorable environment within a modest warm sector as you move east of the Appalachian front. Shear profiles across the Mid Atlantic are anticipated to be greatest north of the Mason Dixon, however shear magnitudes are still capable for enabling stronger mid-level mesocyclones to materialize and hold as far south as I-66 leading to prospects for heavier thunderstorms to hold across the urban corridor extending from northern VA up through NYC and western LI. HREF probs for >1" are pretty high for both the neighborhood and EAS fields meaning there's a consensus for areas of heavy rainfall to impact much of the Mid Atlantic with the most pronounced signatures into the Central Appalachians and the urban centers, both are which are susceptible to flash flood concerns. Antecedent soil moisture is dry, so the initial burst of rainfall will be beneficial to those areas not tied completely by urban infrastructure, however, there's a sufficient signal in the QPF means to maintain the previous SLGT risk inherited for the region as 00z CAMs maintained their depictions on a multi-round cycle of convection moving into the area with pockets of 2-3+" forecast across portions of the aforementioned areas. ...New England... Shortwave ahead of an approaching disturbance from the southwest will enter the region by late-morning into the afternoon with scattered to widespread showers with isolated pockets of thunder for the initial wave of precipitation during the period. A second wave of precipitation with higher convective potential will enter the area by the second half of the afternoon and evening with heavier rain threat poised to impact portions of central and northern New England with southern New England likely to see more of a benefit from the approaching surface low and associated warm/cold front evolution. Areas of northern and central New England are forecast to see the most rainfall of the setup, however the instability gradient will likely be better situated south of the region as boundary layer theta_E's are likely just below the necessary magnitude to embrace a heavier convective footprint. Still, local pockets of >1"/hr are plausible over New England, north of I-90 with a greater potential for 1-2"/hr closer to the interstate and points southeast. Antecedent soils in southern New England are very dry currently with the watershed running well- below normal which should curb a more pronounced flash flood prospect with generally isolated flash flood signals in more urbanized settings. With that, the MRGL risk inherited remains forecast for much of New England. ...Front Range and Central High Plains... Defined theta_E ridge positioned over the Central to Southern High Plains will lead to an axis of relatively unstable boundary layer conditions conducive for convective generation in tandem with passing shortwaves ejecting out of the Rockies. HREF blended mean QPF depicts a smattering of elevated precipitation outputs with 1-2" totals littered across the High Plains from eastern WY and western SD down through KS/CO and portions of southwest TX. Some of the areas noted for potential impact have been hit recently, so local FFG's are lower than normal for the time frame meaning a bit easier chance at exceeding the FFG markers in place and creating isolated flash flood concerns. Threat is lower end compared to what has transpired in the past few days, but it is the beginning of what will be an active northwesterly flow pattern that could spawn multiple MCS's across the High Plains. The previous MRGL risk inherited was maintained with an extension north into the Badlands of SD and neighboring eastern WY. ...Northern Plains... Potent shortwave dropping out of western Canada will aid in regional amplification of the flow out ahead of the trough with increased ascent located within the diffluent area downstream into eastern MT and northern ND. Sufficient mid-level forcing and instability over the region will allow for scattered convection to materialize during peak diurnal destabilization, generating pockets of heavy rainfall during the late-morning into the early evening before instability wanes. Modest probs (30-50%) for >2" of rain exist within the latest 00z HREF neighborhood fields across the area of northeastern MT into the northern tier of ND with low end probabilities for >3" as some CAMs spawn supercells in-of the Northern High Plains. Previous MRGL was carried over into this update, but did expand the risk into MT to account for the heavy QPF distribution in the CAMs bleeding over into the area with similar FFG markers situated in the area. Kleebauer Day 2 Valid 12Z Tue Jun 23 2026 - 12Z Wed Jun 24 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT OVER PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS TO LOWER MISSISSIPPI VALLEY... ...Central and Southern Plains to Lower Mississippi Valley... The morning period on Tuesday will be one to monitor as lingering heavy convection across the ArkLaTex to the I-20 corridor could enhance flash flood prospects early on in the forecast, a lingering potential that would carry out of the D1 period. Multiple CAMs and even the ML are suggesting heavy rains would carry over from the overnight period into early Tuesday morning with prob fields just north of the DFW metro actually quite impressive for >3" of additional rainfall in the 12z Tue to 00z Wed window, running between 30-60%. This would easily lend to flash flooding capabilities in the urban corridor, even some of the larger towns surrounding due to the prominent urban sprawl in place. This is certainly a period to watch as the evolution from the previous period will dictate the threat in the D2. For now, a SLGT risk was added to encompass the area of greatest concern for the front half of the period. As we head into the afternoon and evening hours, the mid and upper pattern across the Western and Central U.S. will setup into a persistent northwesterly flow regime with multiple shortwave ejections out of the Rockies allowing for a maturation of thunderstorms over the High Plains during peak diurnal instability. From there, organization of thunderstorms are likely to occur as they migrate downstream and mature with sufficient mid-level shear presence to maintain any thunderstorm complex generation. This is a relatively classic MCS pattern for this time of the year with heavy rain prospects likely to occur from the Front Range down through KS/OK, eventually migrating into the Lower Mississippi Valley by the end of the forecast period. Totals on D2 are consistent within the means with 1-2" rainfall coverage encompassing a large portion of the Central High Plains down through OK. This puts emphasis on heavy rainfall over the western half of KS into OK for the period with a chance for locally 3+ inches in some of the hardest hit locations. These areas will have already been subject to heavy rainfall in recent periods, so grounds could still be somewhat saturated and more susceptible to flash flooding upfront. Given the consistent signal and ensemble QPF forecast, a SLGT risk was added across the above area with the heaviest rainfall likely to occur over western KS into northern OK. ...Southeast Virginia... Shortwave ejecting out of the Tennessee Valley will make headway into the southern Mid Atlantic with several pieces of guidance indicating a small focused area of heavy rainfall across the Hampton Roads area of southeast Virginia. The approach of the shortwave trough is aiding in development of a surface low off the VA Capes leading to a narrow corridor of enhanced convergence across the Tidewater during the period Tuesday morning. CAMs are generally aggressive with local maxima between 2-3" across the Tidewater, an area more prone to flash flooding due to urbanization factors present. HREF neighborhood probabilities for >2" are up between 50-70% across the area, a threshold that would be sufficient for flash flood potential, especially when you combine the rate factors of 1-2"/hr most likely in the strongest cell cores given the suitable environment in place. Considering the probabilities and the expectation for locally heavy rainfall, a small MRGL risk was added over southeast VA to account for the threat. Kleebauer Day 3 Valid 12Z Wed Jun 24 2026 - 12Z Thu Jun 25 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT OVER PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS TO LOWER MISSISSIPPI VALLEY... A repeat from the D2 pattern will ensue for the afternoon and evening time frame Wednesday with another round of upscale growth from convection that matures over the High Plains and slides southeast within the prevailing northwesterly flow aloft. This threat seems to have a bit more of an emphatic tone to it thanks to models depicting a stronger mid-level disturbance ejecting out of the Rockies this period which would provide greater magnitude for any organized convective regime that occurs. Models are also trying to focus some training convection across portions of the area between northeast OK into the Ozarks of MO/AR in conjunction to the previous complex moving through the area. Upwind vectors are favored for back-building potential in the region when assessing forecast soundings with some models incredibly aggressive with the QPF output in the time frame between 12z Wed and 00z Thu. There's still some discrepancy in the magnitude and exact placement of the training/back-building regime, however this is a pattern where a setup like this is favored, so it will bear watching. For the time being, a SLGT risk was added to D3 across the Central High Plains down through portions of the Southern Plains to the Lower Mississippi Valley. The alignment of the risk matches the recent First Guess Fields for the period and correlates with the precip maximum positioned within the ECENS and EC-AIFS ensemble forecasts. Kleebauer Day 4 and Day 5 Valid 12Z Thu Jun 25 2026 - 12Z Sat Jun 27 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PARTS OF THE CENTRAL PLAINS TO THE OZARKS ON THURSDAY... Day 4...By Thursday the upper pattern is expected to remain mostly zonal across the central U.S. as troughing exists over the Great Lakes and a deeper trough approaches the Pacific Northwest. Meanwhile, subtle shortwaves rounding an upper high over northern Mexico and eventually tracking eastward across the Great Basin and central Rockies Thursday will eject into the central Plains. A frontal boundary will also be positioned across the central Plains and connected to a surface low over the Great Lakes. This will provide a focus for scattered thunderstorms to occur over the central United States. Moisture is forecast to pool along this boundary and PWs should remain around 2", which will allow for any thunderstorms to contain intense rainfall rates. Latest deterministic and ensemble guidance highlight a swath of 2-3" QPF from central KS and northern OK to the mid-Mississippi Valley. Given the convective mode locally higher totals are expected. NBM and ECENS ensemble probabilities are 30-60% for at least 1" of rainfall in this region. Uncertainty remains with respect to mesoscale details and won't be resolved for a few more days, but synoptically there is potential for the frontal boundary and heavy rain to fall north of the current SLGT risk. This will be monitored with future updates. Additionally, this part of the country has received heavy rainfall recently and is forecast to receive more prior to the day 4 forecast period, so antecedent ground conditions will support the potential for scattered flash flooding. Increasing moisture and IVT over the central Great Basin provides some risk for rainfall and locally heavy rain over the sensitive slot canyon region of Utah and northern Arizona, but mean layer flow appears fast enough at the moment to limit the flash flood threat. Day 5...Deepening upper trough over the Pacific Northwest on Friday increases downstream ridging and shifts the heavy rainfall threat along the aforementioned frontal boundary east-northeast from the Ozarks to the Ohio Valley. Less signal and focus for heavy rainfall exists compared to day 4, thus the MRGL Risk in place. However, NBM and ECENS probabilities for at least 1" of rain are between 20-40% and PWs do remain near the 90th climatological percentile, so future upgrades are possible should convection organize along the frontal boundary and overlap with wet antecedent ground conditions. Snell 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 $$