317
FXUS02 KWNH 020648
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 AM EDT Sat Aug 2 2025

Valid 12Z Tue Aug 05 2025 - 12Z Sat Aug 09 2025

...Major to Extreme heat threats increasing across parts the
Southwest later next week...


...Overview...

A refreshing upper trough set to settle into the eastern third of
the nation will be periodically reinforced next week by
disturbances dropping southeast across the Plains and Midwest.
This will be to the lee and on the eastern edge of an upper ridge
over the Southwest which is forecast to build and expand by the
middle of next week leading to an increase in heat threats. A wavy
stalled front will support heavy rain threats mainly near the
coastal sections of the Southeast early-mid next week, but as a
Bermuda High begins to build westward, wet weather is forecast to
spread gradually northward up the eastern U.S. through mid-later
next week, albeit with some uncertainty with expansion timing.
Meanwhile, upper troughing is forecast to push through and eastward
from the Northwest with leading fronts forecast to work over the
northern Rockies/Plains and Midwest to fire local thunderstorms.

...Guidance/Predictability Assessment...

The WPC medium range product suite was primarily derived from a
broad composite blend of reasonably well clustered guidance of the
latest GFS/ECMWF/UKMET/Canadian and GEFS/ECMWF/Canadian ensemble
means along with a compatible National Blend of Models and machine
learning guidance. The blend process aims to mitigate numerous
lingering smaller scale/timing variiances as consistent with
individual predictability. This plan maintains good WPC product
continuity in a pattern with overall above normal predictability.

...Weather/Hazards Highlights...

It generally remains the case that a rather expansive cool air
mass will settle into the eastern U.S. for the first week of
August. High moisture content and instability near a front on the
leading edge of this airmass will focus some localized heavy rain
to raise flash flooding risks given wet antecedent conditions. WPC
Excessive Rainfall Outlook (ERO) Marginal Risk areas have been
introduced for Day 4/Tuesday and Day 5/Wednesday for the Southeast
through south-central portions of the Appalachians/Mid-Atlantic.

Farther west, shortwaves rounding into the eastern edge of the
upper ridge from the Rockies/Plains are forecast to interact with
a downstream frontal zone. By early next week, there is a some
trend for the Upper Midwest/Great Lakes then Ohio/Tennessee
Valleys/Midwest to see increasing rain and storms. Overall, rain
and storms are generally forecast to overspread the east-central
U.S. Tuesday and the East mid-later next week into next weekend.

Rain and thunderstorms are expected from southern central Canada to
the Northern Plains and Upper Midwest and vicinity Tuesday and
Wednesday when WPC Day 4/5 Marginal Risk ERO areas are depicted
given likely moisture/instability pooling with shortwave passage.
Activity will spread more across the Great Lakes and Midwest later
next week. Meanwhile, the Four Corners states could see some
increasing monsoon showers underneath the broad ridge, amid the
relatively dry monsoon season especially across Utah/Arizona.

Cooler than average temperatures are likely on the cool side of
the main frontal system over the central to eastern U.S. next week
and slowly moderate through the period. The Southeast and much of
the central U.S. can expect highs of 5-10 degrees below average
into early next week, with locally greater anomalies, as highs
only reach the 70s and low 80s for parts of the Southeast. These
temperatures should gradually warm closer to normal as the week
progresses. The Northwest will also generally be cooler than
average under rounds of upper troughing. Meanwhile across the
Southwest, dangerous heat will build throughout the week with some
location high temperatures as high as 110-115F, equating to major
to extreme HeatRisk. Temperatures will also be warming to above
normal into the southern and central High Plains as the upper ridge
expands. Some record high temperatures there could be challenged
and eclipsed through mid-later next week. Florida is forecast to
see seasonable temperatures in the 90s, but with ample humidity
allowing for some areas of Major HeatRisk there as well.

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 (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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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