571
FXUS02 KWBC 031947
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Thu Sep 3 2026

Valid 12Z Sun Sep 06 2026 - 12Z Thu Sep 10 2026


...Dangerous late-summer heat wave lingers for the central/
southern Plains to the Mid/Lower Mississippi Valley early next
week...

...Overview...

A strong upper ridge over the central U.S. this weekend weakens
and suppresses south to the entire southern tier through the middle
of next week. Meanwhile, low pressure over the Pacific Northwest
Sunday tracks through Montana Monday then across the Canadian
Prairies into Wednesday before tracking over the northern Great
Lakes Thursday. Moisture streams over the Intermountain West and
especially up the Great Plains ahead of this low setting up heavy
monsoonal rains Sunday and Plains rains on Monday. The heavy rain
threat then shifts east from the northern Plains to the Great Lakes
through midweek.


...Guidance/Predictability Assessment...

The position and movement of the Northwest low drove model
preference this morning. Good agreement between the 06Z EC-AIFS
and 00Z CMC Days 3-5 warranted a model blend weighed toward them
and the 00Z ECMWF. The GFS and UKMET were a bit out of phase with
the consensus, though that improved with 12Z. By Day 6, the CMC was
an outlier with a strong low reaching the northern CA coast, so the
preference for Days 6/7 was the EC-AIFS and ECMWF. The 12Z
physical consensus is now for low pressure near northern CA by
Wednesday morning, though the 12Z EC-AIFS is general troughing off
CA, so that will need to be monitored. The forecast for later in
the week depends on movement of this western trough vs the southern
tier ridge. The EC-AIFS maintains a farther west ridge over the
Four Corners states while the physical model consensus is ridging
shunted farther east due to the trough moving across CA.


...Weather/Hazards Highlights...

Heat focuses over the Mid/Lower Mississippi Valley to southern
Texas by early next week. Some Extreme HeatRisk persists due to
higher min temps than normal for September. Key Messages remain in
effect, though the greater concern for now is into the weekend with
less certainty about how extreme the temperatures will be for
the first part of next week.
Meanwhile, cooler temperatures over the Ohio Valley, Mid-
Atlantic, and Southeast linger through Labor Day before uncertainty
reigns as to the position of the southern ridge axis. Cooler than
normal temperatures will also persist for much of the western U.S.
for early next week under the trough and potentially lasting
through next week depending on the trough axis position.

Monsoonal moisture peaks for the Southwest and Intermountain West
Sunday with diurnally driven activity from southern CA through the
central Rockies. Strong Gulf moisture surging up the Plains
causes heavy rain from Montana Sunday night, the Dakotas on Monday
and Minnesota on Tuesday.


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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