261 FXUS02 KWBC 221958 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EDT Sat Aug 22 2026 Valid 12Z Tue Aug 25 2026 - 12Z Sat Aug 29 2026 ...Hazardous heat to continue from the Lower Mississippi Valley across the Southern Plains to the Desert Southwest... ...Overview and Guidance/Predictability Assessment... The latest suite of guidance maintains a well clustered large scale pattern of a strong high anchored over the Southwest along with a mean upper trough over the east-central U.S. through the extended period. This pattern will have little change as the week progresses and as such, will support a multi-day heatwave for much of the southern tier states. Hazardous heat will be the most prominent for the Southern Plains and Lower Mississippi Valley. Along the ridge's periphery monsoonal moisture will promote scattered convection across the Intermountain West and Rockies and strong convection with local downpours spill across parts of the central states. Shortwaves will maintain upper troughing over the east-central U.S. to favor wavy and moderating frontal surges. Wrapping rains lingering over the Northeast early next week as a lead low pulls away will be followed by broad periods with organized rain/thunderstorms for portions of the East/Southeast the rest of the week with wavy frontal systems. ...Weather/Hazards Highlights... Daily maximum temperatures Under the high pressures daily temperatures across the south will climb into the 90s and 100s with oppressive heat indices. Record- breaking warm overnight temperatures across the southern tier will further limit recovery from the heat, especially given heatwave longevity which may continue to heat related illnesses. Widespread Major to Extreme HeatRisk will persist in the Southern Plains and Lower Mississippi Valley. For the Desert Southwest day maximums may easily soar to/above the 110s which could also cause heat concerns next week. Areas of the Southeast may reach a few degrees above normal at times with moist dewpoints and high heat indices. Please see WPC's Key Messages for more details on the extreme heat. Elsewhere, most areas will see near average temperatures, with the Ohio Valley and vicinity below average. The interior Northeast will have continued chances for overcast skies and wrapping rains as the upper low makes a slow exit. Meanwhile, monsoonal moisture will be streaming northward along the periphery of the upper ridge and will help trigger scattered, diurnally driven convection to the Intermountain West and Rockies. Individual cells may lead to isolated instances of flash flooding for sensitive locations such as burn scars, favored terrain like slot canyons and urban areas. WPC maintains a Marginal Risk for excessive rainfall for both Tuesday and Wednesday. Shortwaves rounding the top of the ridge will trigger showers and thunderstorms across the central U.S. and will shift southwest with time. Some of these storms will be strong, possibly severe, however the exact location and timing remains a bit uncertain. Given the frontal proximity and a pooling moisture/instability focus over the Central Plains, WPC has Marginal Risk for excessive rainfall areas in place. Organized rain/thunderstorm chances from the Midwest/Great Lakes early-mid next week will with wavy frontal pushes increasingly spread over a hot/moist/unstable East/Southeast next week thus maintaining Marginal Risk areas for Tuesday/Wednesday given repeat multi-day potential. Campbell/Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$