401 FXUS02 KWBC 041953 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 353 PM EDT Fri Sep 4 2026 Valid 12Z Mon Sep 07 2026 - 12Z Fri Sep 11 2026 ...Prolonged late-summer heat wave lingers for the central/ southern Plains to the Mid/Lower Mississippi Valley through much of next week... ...Overview... An upper low over the Northwest on Monday will round the top of a persistent southern tier ridge, tracking over the Canadian Prairies to James Bay by Wednesday. This system brings a threat for heavy rainfall to the far Northern Plains/Upper Midwest Monday and general showers to the Great Lakes/Northeast Tuesday/Wednesday. Troughing develops off the California Coast midweek which likely means less direct moisture from Marie into the western U.S. late in the week than prior forecasts. ...Guidance/Predictability Assessment... Guidance is fairly agreeable Days 4/5 with the low tracking from Idaho Monday to Manitoba Tuesday with timing uncertainty from there as it tracks across eastern Canada. The 12Z GFS/UKMET slowed their solutions, making for a decent 12Z consensus there. Certainty also improved California through the middle of next week with a more offshore solution to the low, particularly with a west shift from the CMC. As of this morning, the preference for a 06Z EC-AIFS/00Z ECMWF solution is holding with better agreement from the rest of the 12Z global deterministic suite. The 13Z NBM QPF was amended mainly with the 00Z ECMWF and 06Z EC-AIFS/GFS which enhanced QPF over the northern tier Days 4/5 and reduced QPF (sourced from Marie) over the western U.S. Days 5-7. However, the tropical moisture plume is broad, so some enhanced rainfall is possible, but that may be next weekend. ...Weather/Hazards Highlights... The long duration Heat Wave is now expected to linger over Mid/Lower Mississippi Valley to southern Texas through much of next week with a secondary peak intensity around Wednesday. Key Messages remain in effect with several forecast record highs forecast. Cooler than normal temperatures on tap for early next week under the low/trough, though those moderate with the ridge expanding over much of the southern U.S. reaching into the Southwest. The upper low through the northern tier will bring Monday/Tuesday heavy rain threats from the Northern Plains through the Upper Midwest. Rainfall of a more general variety will continue to accompany this system as it slides through the Great Lakes and Northeast as this area is post frontal/cooler. Monsoonal moisture will continue for the southern Rockies through midweek. Tropical moisture from Marie looks to generally remain offshore from California, though uncertainty still remains with this plume. Jackson 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 $$