401
FXUS02 KWBC 041953
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Fri Sep 4 2026

Valid 12Z Mon Sep 07 2026 - 12Z Fri Sep 11 2026


...Prolonged late-summer heat wave lingers for the central/
southern Plains to the Mid/Lower Mississippi Valley through much of
next week...

...Overview...

An upper low over the Northwest on Monday will round the top of
a persistent southern tier ridge, tracking over the Canadian
Prairies to James Bay by Wednesday. This system brings a threat
for heavy rainfall to the far Northern Plains/Upper Midwest Monday
and general showers to the Great Lakes/Northeast Tuesday/Wednesday.
Troughing develops off the California Coast midweek which likely
means less direct moisture from Marie into the western U.S. late
in the week than prior forecasts.

...Guidance/Predictability Assessment...

Guidance is fairly agreeable Days 4/5 with the low tracking from
Idaho Monday to Manitoba Tuesday with timing uncertainty from there
as it tracks across eastern Canada. The 12Z GFS/UKMET slowed their
solutions, making for a decent 12Z consensus there. Certainty also
improved California through the middle of next week with a more
offshore solution to the low, particularly with a west shift from
the CMC. As of this morning, the preference for a 06Z EC-AIFS/00Z
ECMWF solution is holding with better agreement from the rest of
the 12Z global deterministic suite. The 13Z NBM QPF was amended
mainly with the 00Z ECMWF and 06Z EC-AIFS/GFS which enhanced QPF
over the northern tier Days 4/5 and reduced QPF (sourced from
Marie) over the western U.S. Days 5-7. However, the tropical
moisture plume is broad, so some enhanced rainfall is possible, but
that may be next weekend.


...Weather/Hazards Highlights...

The long duration Heat Wave is now expected to linger over
Mid/Lower Mississippi Valley to southern Texas through much of next
week with a secondary peak intensity around Wednesday. Key
Messages remain in effect with several forecast record highs
forecast. Cooler than normal temperatures on tap for early next
week under the low/trough, though those moderate with the ridge
expanding over much of the southern U.S. reaching into the
Southwest.

The upper low through the northern tier will bring Monday/Tuesday
heavy rain threats from the Northern Plains through the Upper
Midwest. Rainfall of a more general variety will continue to
accompany this system as it slides through the Great Lakes and
Northeast as this area is post frontal/cooler. Monsoonal moisture
will continue for the southern Rockies through midweek. Tropical
moisture from Marie looks to generally remain offshore from
California, though uncertainty still remains with this plume.


Jackson


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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