622 FXUS02 KWBC 080642 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 242 AM EDT Tue Sep 8 2026 Valid 12Z Fri Sep 11 2026 - 12Z Tue Sep 15 2026 ...Prolonged late-summer heat wave lingers for the southern Plains through next weekend... ...Overview... A shortwave will push a cold front from the Northern Plains to the Northeast Friday to Sunday, with increasing rain chances along and ahead of it. Behind this, consensus is increasing for a compact closed low to move into the Northwest by Saturday, progressing eastward into the Northern Plains by Monday. Moderate to heavy rainfall looks increasingly likely across the Upper Mississippi Valley to Great Lakes Sunday and Monday, with some winter weather potential for the Northern Rockies. Upper level ridging will meanwhile persist across the southern tier, maintaining hot conditions for the south-central U.S. and monsoonal moisture for the Southwest. Another shortwave moves into the Northwest next Tuesday. ...Guidance/Predictability Assessment... Guidance is showing better agreement on the overall pattern through much of the period compared to previous cycles. There are some very minor timing differences with the first shortwave as it slides through the northern tier early in the period. By Saturday, an upper low will drop into the Pacific Northwest with the majority of guidance now showing distinct separation of this low with another upper low well off the West Coast. The exception is the CMC which still shows some interaction and thus a slower progression of the system eastward. As the system moves into the Northern Rockies and eventually the Plains, timing uncertainties do increase, but the GFS and ECMWF are most consistent with ensembles. The WPC forecast was based on a non-CMC blend for the first half of the period, incorporating the ECENS to 40 percent by Day 7 to help mitigate the harder to resolve detail differences at this longer time range. Overall maintained good agreement with the previous WPC forecast as well. ...Weather/Hazards Highlights... The long duration heat wave is expected to linger over the Mid/Lower Mississippi Valley and southern Plains into the medium range period with widespread Major to Extreme HeatRisk. Key Messages remain in effect with several record minimum and maximum temperatures in the forecast. There continues to be a trend for relief to northern areas by the weekend, confining the greatest heat threat to the southern Plains. Above normal heat may also build briefly across the Southwest and parts of California into late week as upper level ridging extends into the region. This southern ridge will also help support monsoonal moisture and daily shower and thunderstorm chances for the Four Corners region much of the period. A cold front will be exiting the Northeast by Friday, but lingers across the Southeast supporting daily showers and thunderstorms, with locally heavy rainfall possible. Behind this, another front will bring rain to the Midwest and into the Northeast Friday- Sunday. The main focus for precipitation during the period will be across the Northwest into the Northern U.S. this weekend and early next week as an upper low moves through. A strong cold front will enhance rainfall chances ahead of it, with moderate to heavy rainfall potential increasing by Sunday and especially Monday across the Midwest. Wintry weather will also be possible in the northern Rockies this coming weekend as cooler air moves in behind the cold front. Santorelli 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 $$