512 FXUS02 KWBC 011938 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 338 PM EDT Tue Sep 1 2026 Valid 12Z Fri Sep 04 2026 - 12Z Tue Sep 08 2026 ...Dangerous late-summer heat wave will continue across parts of the central U.S. into early next week, but ease in the Southeast late this week... ...Overview... Dangerously hot weather will continue across much of the central U.S. through the weekend into early next week, while a cold front will bring relief to parts of the southern Mid-Atlantic/Southeast after a couple more very hot days on Friday and Saturday. In contrast, persistent troughing should keep much of the Pacific Northwest cool, showery, and unsettled into early next week. Locally heavy rainfall and severe weather are possible along a frontal zone from the Midwest to the Ohio Valley, central Appalachians, and Mid-Atlantic on Friday, with possible chances farther south into the Carolinas on Saturday. Monsoonal moisture returns late week into the weekend with a tropical connection potentially leading to enhanced rainfall for parts of the Southwest into next week. ...Guidance/Predictability Assessment... Deep troughing along the West Coast, highly amplified ridging over the central U.S., and more troughing along the East Coast will continue to be the dominant features of the large scale pattern into early next week. Models are generally in good agreement with the pattern through most of the weekend, but uncertainty increases leading into next week. The first notable model difference in the 12Z model cycle primarily stems from timing/placement of one shortwave ejecting eastward from the Northwest low atop the ridge Sunday-Monday. The GFS keeps this strong enough (potentially combining with Canadian energy digging) to suppress the ridge in the northern tier early next week, unlike consensus. Then the track of the Northwest trough slowly eastward as it opens up is also somewhat questionable, but did see that the 12Z AIFS now jumped west and matches better with consensus, after earlier AIFS runs were east. Additionally, the evolution of the western U.S. troughing will have implications on the future track of eastern Pacific tropical system Marie. Older GFS runs in particular have been outliers in showing Marie's track moving near/into southern California and the Southwest. Newer runs have trended away from this solution more toward the non-NCEP and AI consensus. Though a handful of ensemble members (GEFS and EC both) still allow for this type of track, so NHC and WPC will continue to monitor. Model preference continues to lean away from the GFS solutions (now for the northern tier, previously for the Marie track), and toward the EC/CMC, AI models, and increasing proportions of the ensemble means as the period progressed. ...Weather/Hazards Highlights... Intense late-summer heat will continue across the central U.S. through the weekend into next week as a large mid/upper ridge dominates the region. The well above normal temperatures combined with high humidity and very warm overnight lows in the mid 70s will result in widespread areas of Major to Extreme HeatRisk and a concern for heat-related illnesses. Hot conditions are also forecast across the Ohio Valley, Mid-Atlantic, and Southeast late this week, but should gradually lessen in magnitude/coverage over the weekend as a cold front drops in from the north. Please continue to see WPC's Key Messages for more details on this long lasting heat wave. In stark contrast from the heat across the central and eastern U.S., cooler than normal temperatures will remain in place across the Northwest through early next week as persistent clouds and showers associated with deep troughing over the West Coast linger over the region. High temperatures will mostly top out in the 50s, 60s, and 70s, which is roughly 10-15 degrees below seasonal norms. The frontal system that will bring relief from the heat across parts of the eastern U.S. this weekend will first interact with sufficient moisture and instability to produce locally heavy rainfall and severe weather from the Midwest to the Ohio Valley, central Appalachians, and Mid-Atlantic on Friday. Some, though perhaps lesser, chances for severe weather and flooding concerns are possible farther south into the Carolinas on Saturday. The strongest storms will be capable of producing damaging winds, and perhaps some hail and a few isolated tornadoes. Storms could also contain heavy rain rates that could lead to scattered instances of flash flooding. Surging monsoonal moisture will foster more numerous showers and thunderstorms across parts of the Southwest/Four Corners states on Friday, with potential for isolated to scattered flash flooding. Farther north, rain is forecast for the Pacific Northwest to northern Rockies underneath the upper low, with a nonzero flooding chance as well. Rain chances should persist in these areas into Saturday. More surges of moisture are likely Sunday and Monday, with coverage likely combining across the Intermountain West, with some possible tropical connection to Marie. While the current thinking favors a track for Marie that stays far away from southern California, there is still a threat of tropical moisture enhancing monsoonal rainfall and thus leading to additional concerns for flash flooding. Stay tuned to NHC and WPC for updates. Tate/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 $$