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




$$