198
FXUS02 KWBC 240728
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Mon Aug 24 2026

Valid 12Z Thu Aug 27 2026 - 12Z Mon Aug 31 2026


...Hazardous Heat continues from the Desert Southwest to the
Southern Plains...

...Overview...

The upper level pattern will feature troughing in the Northwest and
East with a strong ridge anchored over the Southwest. The ridge
will flatten late this week as upper level troughing strengthens
over the Northwest, resulting in some areas seeing relief from the
ongoing heat wave, but hazardous heat will persist for the Desert
Southwest and southern Plains. Moisture on the western periphery of
the ridge will continue to support daily monsoonal convection
across the Intermountain West. Meanwhile, several frontal systems
will push through the upper troughs, bringing showers/thunderstorms
from the northern/central Plains to the East/Southeast U.S..

...Guidance/Predictability Assessment...

Guidance agrees that an ongoing upper pattern highlighted by a
strong Southwest U.S. to southern Plains high/ridge anchored by
mean troughs near the Pacific Northwest and the east-central U.S.
will persist over the next week. This will continue to support a
protracted heatwave with Hazardous Heat threats from the South-
Central to Southwest U.S.. Along the ridge`s periphery monsoonal
moisture may promote scattered convection from the Southwest to the
Rockies, with convection also working into the north-central U.S..
Shortwaves will maintain upper troughing over the east-central
U.S. to favor wavy and temperature moderating frontal surges.
Expect unseasonally well organized rain/thunderstorms daily as
wavy fronts push into and stall over the East/Southeast and pool
deep moisture and instability.

A broad model/ensemble mean and machine learning guidance blend
seems to provide a solid forecast basis with good product and
messaging continuity given favorable clustering trends that have
further improved with the latest 00 UTC guidance.

...Weather/Hazards Highlights...

Still under the influence of the upper high/ridge, daily maximum
temperatures across the southern Plains will continue to rise into
the 90s and 100s with oppressive heat indices. Record- breaking
warm overnight temperatures across the southern tier will further
limit recovery from the heat, especially given heatwave longevity
which may result in heat related illnesses. Conditions will improve
this week for the Lower Mississippi Valley, but widespread Major
to Extreme HeatRisk will persist in the southern Plains. For the
Desert Southwest, daytime max temperatures are forecast to soar
into the 110s, which will create heat concerns this week. Pre-
frontal areas of the Southeast may be a few degrees above normal,
but forecast precipitation and cloud cover will help keep heat in
check. Please see WPC`s Key Messages for more extreme heat details.

Monsoonal moisture streaming northward on the periphery of the
upper ridge will fuel scattered, diurnally driven convection from
the Southwest to the Rockies. Individual cells may lead to isolated
instances of flash flooding for sensitive locations such as burn
scars, favored terrain like slot canyons, and urban areas. There is
a Marginal Risk for parts of these areas in the WPC Day 4/Thursday
and Day 5 Friday Excessive Rainfall Outlooks (EROs).

Shortwaves rounding the top of the ridge to the east-central U.S.
mean upper trough will periodically trigger showers and some strong
thunderstorms from the northern and central Plains to the Midwest
this week. A Marginal Risk ERO covers this threat. Downstream,
elongated ERO Marginal Risk areas are highlighted for portions of
the Southeast and Mid-Atlantic that may see repeated rounds of
locally heavy precipitation as wavy frontal boundaries approach and
ultimately stall over these regions.

Later period, a stronger frontal system will push across an
unsettled Northwest and north-Central U.S., bringing increasing
precipitation chances and potentially heavy rainfall to the Plains
and Midwest. Warm, southerly flow on the southern side of the
system may increase heat for the south-central U.S. next weekend.


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







$$