657
FXUS02 KWBC 270754
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Mon Jul 27 2026

Valid 12Z Thu Jul 30 2026 - 12Z Mon Aug 3 2026

***Long duration heat wave expected for much of the Western U.S.
 and western High Plains***


...Pattern Overview...

The main theme going into the middle of the week will be a large
upper ridge situated across the Rockies and western High Plains
that will result in a lengthy heat wave. An upper trough with a
closed low is expected over the Northeast Pacific, and an
amplified trough will be departing the Northeast states with the
heaviest rainfall exiting the coast. General troughing likely
continues for the East Coast as a second trough amplifies over the
Midwest and brings additional prospects for showers and storms.

...Guidance/Predictability Assessment...

The 00Z model guidance suite features good overall synoptic scale
agreement across the Continental U.S. to close out the work week,
with the best agreement noted on the closed upper high positioned
across the interior Western U.S. through the weekend. The guidance
has started coming into better focus with a shortwave trough
tracking from the Upper Midwest to the Tennessee Valley through
early Sunday, with the GFS slightly more progressive in bringing
the trough southward. The UKMET differed the most with a stronger
surface low over Illinois by Saturday morning, whereas the model
consensus is farther south and weaker. There is also improved
agreement with the northeast Pacific closed low/trough that moves
inland across southern Canada by Sunday into Monday, although the
GFS/GEFS is a little less amplified than the ECMWF/CMC across
Montana and Idaho. The ensemble means were gradually increased to
about 40% by next Monday.

...Weather/Hazards Highlights...

The coastal low that will be affecting the Northeast U.S. for the
middle of this week will slowly exit the region and take most of
the heavy rainfall out to sea by Thursday afternoon. Lingering
showers and breezy conditions will remain across New England
through Thursday night. The area with the heaviest rainfall to
close out the work week will likely be across the Midwest as a
shortwave disturbance aloft promotes the development of mesoscale
convective complexes that will likely bring multiple rounds of
heavy rainfall and strong thunderstorms, with a Slight Risk of
excessive rainfall extending from eastern South Dakota to Illinois
over the Thursday to Friday time period.

Additional heavy rainfall is likely across portions of the Deep
South and Gulf Coast region going into next weekend as a frontal
boundary stalls out across the region, and showers/storms become
more widespread for the Eastern U.S. by Sunday and into Monday.
Daily afternoon and evening thunderstorms are expected from the
central Rockies to the Desert Southwest through Saturday, with
slightly less monsoonal moisture expected into Sunday and Monday
as the upper high expands over the region.

Widespread heat will continue to make weather headlines across a
large portion of the western and central U.S. as a large upper
ridge becomes parked over the southwestern quadrant of the country.
The most extreme heat is expected over the lower elevations of the
Desert Southwest through much of the forecast period, with highs
well into the 110s and approaching 120 degrees in some instances,
and readings near 100 degrees extending north into southern Idaho
and westward to include the Central Valley of California. Another
area of excessive heat is likely from Montana into western portions
of the Dakotas with highs reaching or surpassing 100 degrees next
weekend before a cold front passes through early next week. Hot and
humid conditions will continue through the end of the week across
the Gulf Coast region, with heat indices on the order of 105-115
degrees with dewpoints well into the 70s south of the stalled
front. A slight abatement in the heat is likely by the weekend with
more clouds and rainfall across the region.


Hamrick




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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