069 FXUS02 KWBC 281956 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 356 PM EDT Fri Aug 28 2026 Valid 12Z Mon Aug 31 2026 - 12Z Fri Sep 04 2026 ...Dangerous heat will expand over the South-Central to Eastern U.S. through next week... ...Pattern Overview... An intensifying late summer heat wave will bring extreme temperatures to the Central/Southern Plains before expanding to the Midwest and South next week. Meanwhile, surges of monsoonal moisture will continue to support daily showers and thunderstorms across portions of the Southwest and the Intermountain West/Rockies with localized flash flooding possible. Farther north, a progressive series of storm systems will bring active weather to the Pacific Northwest, along with the potential for severe weather and heavy rain threats farther downstream from the Northern Plains and Upper Midwest to the Northeast. ...Guidance/Predictability Assessment... Models are in reasonably good agreement on the synoptic scale pattern during the medium range period. Guidance accurately capture the strength and location of the Southern U.S. ridge, as well as the timing of a digging West Coast trough. There's uncertainty around the depth of the West Coast trough, as well as timing and depth questions around a northern tier/southern Canada disturbance next week. A general model blend consisting of the AiGFS, ECAIFS, deterministic Euro/GFS and CMC were used in the day 3 blend. The AiGFS is replaced with the UKMET due to the UKMET clustering better with consensus on the location of embedded shortwave energy in the Lower Mississippi Valley. The Euro is not utilized on day 5 due to it presenting a more progressive shortwave ejecting out over the Great Basin/Intermountain West than consensus. The ECENS, GEFS and CMCE are favored in the blend on days 6 and 7 to mitigate trough uncertainties in the West and Northeast. ...Weather/Hazards Highlights... A sprawling upper ridge expanding from the Central U.S. to the Southeast U.S. will focus an intensifying and long-lasting late summer heat wave from the central/southern Plains to the Midwest, Southeast, and Deep South next week. High temperatures climbing well into the 90s and 100s combined with high humidity and very warm overnight lows in the 70s to near 80 will result in widespread areas of Major to Extreme HeatRisk, increasing the threat of heat related illnesses. Please see WPC's Key Messages for more details. Surges of monsoonal moisture ahead of persistent Pacific Northwest upper troughing and Central/Eastern U.S. upper ridging will continue to fuel daily scattered afternoon and evening showers and thunderstorms across portions of the Southwest, Intermountain West, and Rockies through most of next week. Some thunderstorms are likely to produce heavy rainfall which may lead to isolated instances of flash flooding for more vulnerable areas like burn scars, slot canyons, and urban areas. A series of disturbances tracking into the Pacific Northwest and along the U.S./Canada border will highlight a period of active weather across the northern tier of the country over the course of next week. A potent shortwave/closed upper low moving from south- central Canada eastward to northern New England and vicinity will lead to the development of a strengthening surface low and frontal system with the potential to bring heavy rainfall and severe weather across parts of the northern Plains, Upper Midwest, Lower Great Lakes, Ohio Valley and the Northeast. A multi-day rainfall event beginning Monday night and continuing through Thursday may produce flash flooding over portions of the interior Northeast. Meanwhile, persistent troughing and reinforcing shortwaves crashing into the Pacific Northwest coupled with a possible atmospheric river may result in a period of heavier rainfall for coastal and mountain regions of Washington and Oregon mid to late next week. Additionally, some snow can't be ruled out across the highest elevations of the Cascades as a pocket of colder air aloft moves overhead. Elsewhere, dissipating frontal boundaries and a slow-moving upper low will likely contribute to a lingering threat for locally heavy rainfall and isolated flash flooding concerns over portions of the Gulf Coast, Southeast, and Florida next week. Kebede/Miller 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 $$