376
FXUS02 KWBC 100755
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Thu Sep 10 2026

Valid 12Z Sun Sep 13 2026 - 12Z Thu Sep 17 2026


...Late-summer heat lingers over the southern Plains as heavy rain
threat emerges across the upper Midwest to the upper Great Lakes
early next week...


...Overview...

A compact closed low moving through the Pacific Northwest this
weekend is forecast to eject across the northern Plains on Monday
bringing a swath of moderate to heavy rainfall across the upper
Midwest to the upper Great Lakes Sunday and Monday, with wet snow
possible over the higher elevations of western Montana. Meanwhile,
upper level ridging will persist across the southern tier,
maintaining hot conditions for mainly the Southern Plains, with
monsoonal thunderstorms for the Four Corners states. A closed low
aloft could develop and linger off the West Coast by midweek next
week.


...Guidance/Predictability Assessment...

While the guidance was generally agreeable on the overall pattern
through the period there were some notable timing/evolution
differences on the main features. A compact mid- and upper-low is
forecast to traverse the northwestern U.S. this weekend before
ejecting across the northern Plains on Monday. All global models
except the CMC depicts this scenario together with firm support
of the ensemble means from the ECMWF, GEFS, and CMC means. The
deterministic CMC appears to be the outlier by digging a much
deeper trough through the Northeast early next week. Overall, model
consensus has trended northward with the swath of enhanced
rainfall across the upper Midwest to the upper Great Lakes from
Sunday into Monday. In addition, a better agreement on the
ejection of the compact closed low has increased the chance for the
heat to build across the South to the central High Plains this
weekend before spreading northeast into the upper Midwest on
Monday and further downstream toward the Northeast by Tuesday.
Thereafter, it appears that the consensus of the ensemble means
agree with a generally zonal upper-air pattern across the northern
tier states heading into the latter half of next week.

The WPC medium-range forecast charts and grids are based on the
consensus blend of 40% 12Z EC/EC mean, 40% 18Z GFS/GEFS, and 20%
from the 12Z CMC mean. This blend yields forecasts compatible with
the previous WPC forecast package. Main edits to the NBM were to
increase the temperature contrasts on either sides of the fronts
traversing the northern tier states through the medium-range
period. The NBM QPFs were largely unchanged except narrowing down
the lighter QPFs on either side of the fronts, and smoothing out
the QPF blobs on Days 6 and 7.


...Weather/Hazards Highlights...

Heat will remain in the forecast into the medium-range period
across much of the southern tier of the country where broad upper-
ridging remains in place. There appears to be an increasing chance
for the heat to spread northeastward across the Midwest and
smaller window of opportunities for the heat to spread further
downstream into the Northeast. The greatest coverage of Moderate to
Extreme Heat Risk will focus on the southern Plains/Texas into the
lower Mississippi Valley. This southern ridge will also help
support monsoonal moisture and late-day shower and thunderstorm
chances for the Four Corners region through much of the period.
There looks to be an uptick in the influx of moisture early next
week as the southern ridge shifts eastward with a greater chance
for locally heavy rainfall/flash flooding.

Lingering moisture over the Southeast will continue a daily threat
for showers and thunderstorms, including the Sunshine State.
A compact closed low moving through the Pacific Northwest this
weekend is forecast to eject across the northern Plains on Monday
bringing a swath of moderate to heavy rainfall across the upper
Midwest to the upper Great Lakes Sunday and Monday, with wet snow
possible over the higher elevations of western Montana. The strong
cold front sweeping through the northern Plains will also bring a
round of strong thunderstorms through the central Plains to the
Midwest later on Monday. The front is forecast to become more zonal
by midweek with rounds of showers and thunderstorms stretching
from the central Plains to the Mid-Atlantic and New England.

As the heat persists across the South with brief opportunities for
it to spread further northeast, general troughing across the
Pacific Northwest will likely keep temperatures below normal from
California to the interior Pacific Northwest, extending into the
northern Plains through the medium-range period. The Desert
Southwest remains seasonably hot and dry outside of the monsoonal
thunderstorms over the Four Corners.



Kong


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












$$