647 FXUS02 KWBC 062000 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Sun Sep 6 2026 Valid 12Z Wed Sep 09 2026 - 12Z Sun Sep 13 2026 ...Prolonged late-summer heat wave lingers for the central/ southern Plains to the Mid/Lower Mississippi Valley through much of the week... ...Overview... Troughing will extend from Canada into the northern tier of the U.S. later this week, tracking from the northern Plains/Midwest through the Great Lakes and Northeast Wednesday-Friday. This should bring rain chances to these areas south into the Mid-Mississippi Valley, Ohio Valley, and central Appalachians, while primarily diurnally driven scattered thunderstorms will continue across the Southeast. Meanwhile upper ridging will maintain hot conditions across the south-central U.S. through the workweek. Some relief is possible by next weekend, but this will depend on an increasingly uncertain pattern, including the timing and placement of the next upper trough or two coming into the Northwest. ...Guidance/Predictability Assessment... Model guidance starts in good agreement with the pattern described above, and a multi-model blend of the deterministic/AI guidance was able to be used. As the first trough moves through the eastern U.S. Thursday-Friday, this may suppress the warm ridge across the Southeast as least. The next trough should reach the northwestern to north-central U.S. extending from an upper low in central Canada Hudson Bay late week. This low looks to move over Hudson Bay by the weekend while the troughing moves across the Great Lakes and Northeast. These first two troughs mostly show minor model differences. By far, the greatest model spread during the period has been with the evolution of energy diving through the northeast Pacific/western Canada by the weekend. Some guidance including the older 00Z and 06Z GFS runs were indicating that this energy would be joined up with the second trough, causing it to dig across the central U.S. However, most guidance (including the newer 12Z GFS) is now favoring that this energy stays a separate feature from the second trough, forming a closed upper low near British Columbia Friday or atop the Northwest by Saturday (aka a third trough of the period). This upper low shows somewhat better consensus now with the 12Z cycle, though the GFS is still a little on the fast side. However, the CMC and EC-AIFS end up showing a midlatitude Pacific low moving east to combine with that energy, holding it farther west by Sunday. The forecast attempted to go with a middle ground forecast solution, most similar to the ECMWF and EC mean. ...Weather/Hazards Highlights... The long duration heat wave is expected to linger over the Mid/Lower Mississippi Valley to southern Texas through much of the week with widespread Major to Extreme HeatRisk. Key Messages remain in effect with several forecast record minimum and maximum temperatures forecast. The pattern becomes more uncertain by the weekend, but there is some trend for warm temperatures to persist because of the evolution of the upper troughs farther north. An upper and surface low moving through southern Canada will push a cold front through the Northeast/Mid-Atlantic, Ohio Valley, and Mid-Mississippi Valley Wednesday-Thursday, with locally heavy rain possible. On the backside of the system, high winds could linger in the northern Plains into Wednesday. Moisture and instability will also allow for rounds of diurnally driven scattered thunderstorms in the Southeast each day. Some monsoonal moisture will continue for the Southwest and southern Rockies through the period as well. The upper troughs in the Northwest should also allow for rounds of precipitation there by Friday and into the weekend. Some rain could expand across the north-central U.S. next weekend, but the potential for heavy amounts there has trended down given the overall model trends for the troughing described above. Tate/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 $$