638
FXUS02 KWBC 101847
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 PM EDT Thu Sep 10 2026

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


...Hazardous heat over the Southern Plains as heavy rain threat
emerges across the Upper Midwest/Great Lakes early next week...


...Overview...

A closed upper trough/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/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 on the western periphery of the aforementioned ridge
for the Four Corners states. Elsewhere, a closed low aloft could
develop and linger off the West Coast into mid-later next week.

...Guidance/Predictability Assessment...

Latest guidance is generally agreeable on the overall pattern
through the period, albeit with some lingering timing/evolution
differences with embedded features that now seem reasonably
mitigated as consistent with individual predictability with usage
of a multi-model and ensemble mean/machine learning guidance blend.
This plan maintains good threat messaging and product continuity.

...Weather/Hazards Highlights...

Hazardous heat will remain focused across the southern Plains and
less robustly over the southern tier of the country where upper-
ridging remains in place. The greatest coverage of Moderate to
Extreme Heat Risk will focus on the southern Plains 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 where a WPC
Excessive Rainfall Outlook (ERO) Marginal Risk area remains in
place. 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. Meanwhile,
lingering moisture over the Southeast will continue a daily threat
for showers and thunderstorms in a protracted wet pattern,
including with persistent low-level easterly flow into Florida.

A closed upper trough/low moving through the Pacific Northwest
this weekend is forecast to eject across the northern
Rockies/Plains into Monday to drive a lead front and bringing a
swath of moderate to heavy rainfall downstream to the Upper
Midwest/Great Lakes Sunday and Monday, with wet snow possible back over
the cooled higher elevations of western Montana. A broad ERO
Marginal Risk area with an embedded Upper Midwest Slight Risk area
is depicted. The strong cold front sweeping with moderating
temperatures through the northern Plains will also bring a round of
strong thunderstorms through the central Plains to the Midwest
later on Monday. The cooling 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/Schichtel


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














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