547
FXUS21 KWNC 231853
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 23 2026

SYNOPSIS: Model ensembles favor a continuation of extreme heat already under
way across much of the persisting into week-2 tied to anomalous mid-level high
pressure near the Four Corners increasing the chances of above-normal
temperatures across southern Contiguous U.S. (CONUS), which when combined with
Gulf moisture is likely to produce high heat indices east of the Rockies.
Mid-level high pressure is favored to shift eastward and weaken early in the
forecast period, slightly reducing the potential for extreme heat over the
Desert Southwest. Antecedent dryness, combined with little precipitation
favored over the next two weeks supports a Rapid Onset Drought (ROD) risk for
portions of the Central and Southern Plains and Lower Mississippi Valley and
southern areas of the Middle Mississippi Valley.

HAZARDS

High risk of extreme heat for much of the Southern Plains and Lower Mississippi
Valley and southern portions of the Central Plains and Middle Mississippi
Valley, Mon-Tue, Aug 31-Sep 1.

Moderate risk of extreme heat for the Southern Plains and Lower Mississippi
Valley, Central Rockies, and Desert Southwest, as well as portions of the
Central Rockies, Central Plains, Middle Mississippi Valley, Tennessee Valley,
and Southeast U.S., Mon-Wed, Aug 31-Sep 2.

Slight risk of extreme heat across the southern CONUS as well much of the
Central Plains and Middle Mississippi Valley and portions of the Mid-Atlantic
and California, Mon-Sat, Aug 31-Sep 5.

Rapid Onset Drought (ROD) risk for much of the Southern Plains and Lower
Mississippi Valley and adjacent portions of the Central Plains, Tennessee and
Middle Mississippi Valleys, and Southeast U.S.

DETAILED SUMMARY

FOR WEDNESDAY AUGUST 26 - SUNDAY AUGUST 30:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY AUGUST 31 - SUNDAY SEPTEMBER 06: Dynamical model guidance remains in
good agreement regarding subtropical ridging persisting across the southwestern
U.S. through week-2. The 0z ECMWF, GEFS, and Canadian ensembles depict a 594 dm
500-hPa height maximum at the start of the forecast period over the Four
Corners region. Today`s model solutions indicate a slight weakening, as well as
a slight shift eastward of the ridge axis by the middle of week-2. Despite this
weakening however, the synoptic pattern favors a continuation of a late summer
heat wave across much of the southern half of the Lower 48.



The potential for extreme heat is also well-indicated by a variety of forecast
tools. The Probabilistic Extremes Tools (PETs) from the ECMWF and GEFS both
indicate at least a 60% chance of maximum temperatures to exceed the 85th
percentile at the outset of week-2, and a 40% chance of exceeding the same
criteria into the middle of the forecast period. Daily computed heat indices
above 100F are indicated across much of the south-central CONUS through the
middle of the forecast period. As noted earlier, there are some indications of
a weakening of the ridge during week-2 but despite this the signal for
potential extreme heat remains robust. Therefore a high risk of extreme heat is
maintained across much of the Southern Plains and Lower Mississippi Valley and
surrounding regions, valid Aug 31-Sep 1. The high risk of extreme heat has been
discontinued for the Desert Southwest but a moderate risk of extreme heat
remains posted, valid Aug 31-Sep2 for the Desert Southwest, as well adjacent
regions surrounding the high risk area highlighted above. Finally, a slight
risk of extreme heat remains in place surrounding the moderate risk
highlighted, as well as much of the Southeast U.S. and southern portions of the
Mid-Atlantic, valid Aug 31-Sep 5.



A Rapid Onset Drought (ROD) risk remains designated for much of the Southern
Plains and Lower Mississippi Valley and adjacent portions of the Central
Plains, Tennessee and Middle Mississippi Valleys, and Southeast U.S. This ROD
area continues to register 30-day precipitation deficits greater than 2 inches,
with little rainfall forecast during the next two weeks. Much of this ROD area
is also included within the moderate risk of extreme heat as the potential for
increased evapotranspiration rates also looks to reinforce this risk later in
August.

FORECASTER: Danny Barandiaran

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