Valid Saturday August 22, 2026 to Friday August 28, 2026
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM
EDT August 14 2026
Synopsis: A major, long duration period of
extreme heat continues to be predicted across portions of the south-central
contiguous U.S. (CONUS) and Southeast persisting into week-2 tied to anomalous
mid-level high pressure near the Four Corners combined with Gulf moisture to
produce high heat indices. Mid-level high pressure is favored to spread
westward, increasing the risk for extreme heat in 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 Middle and Lower Mississippi Valley.
Hazards - Moderate risk of extreme heat for portions of
the Southern Plains, Lower Mississippi and Tennessee Valleys, and Southeastern
U.S., Sat-Sun, Aug 22-23.
- Slight risk of extreme heat for portions of the Central and Southern
Plains, Middle and Lower Mississippi and Tennessee Valleys, and Southeastern
U.S., Sat-Thu, Aug 22-27.
- Slight risk of extreme heat for portions of the Desert Southwest, Sat-Wed,
Aug 22-26.
- Rapid Onset Drought (ROD) risk for portions of the Central and Southern
Plains and the Middle and Lower Mississippi Valley.
Detailed
SummaryFor Monday August 17 - Friday August 21:
WPC Days 3-7 U.S.
Hazards For Saturday August 22 - Friday
August 28: 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 594-596 dm 500-hPa height
maximum retrograding into the Intermountain West early in the period, with its
amplitude steady or even increasing slightly. As a result, confidence remains
high for a long duration heat event, with many tools indicating the potential
for oppressive conditions lingering well into late August. Both the GEFS and
ECMWF Probabilistic Extremes Tools (PETs) depict at least a 40 percent chance
of maximum temperatures exceeding the 85th climatological percentile through
the middle of week-2 centered across the Central Gulf Coast states. The ECMWF
and GEFS continue to depict a ridge retrogression, now mostly in week-1, with
the ridge axis established over the Four Corners by the start of week-2. A
large contribution from increased humidity is expected, with a strong signal in
the calibrated skill-weighted GEFS-ECMWF heat risk guidance, particularly
across the Central and Southern Plains and adjacent Mississippi Valley where
probabilities exceed 60 percent for maximum heat index values to exceed the
95th climatological percentile in some locations. In addition, the National
Blend of Models (NBM) also depicts a number of locations with nighttime lows
nearing and/or breaking daily records, resulting in little overnight relief
from the daytime heat. A moderate risk for extreme heat remains valid through
Aug 23 and continues to extend into the Southern Plains where there is
increased potential for heat index values to exceed 105 deg F. A slight risk
surrounds the moderate risk area and covers Aug 22-27.
Troughing initially near the West Coast of the CONUS favors an influx of
moisture across much of the western U.S. and enhanced Southwest Monsoon
activity continuing over the Four Corners. However over the last several days a
reduction in signal strength has been noted. With model solutions generally
indicating a weakening of troughing along the West Coast, a gradual reduction
in monsoon activity seems increasingly likely. Therefore the slight risk of
heavy precipitation from yesterday’s outlook has been discontinued. However,
isolated areas of heavy rain remain possible and this region is prone to flash
flooding even with relatively small precipitation accumulations especially
along dry creek beds (arroyos) and in canyons. Caution should always be
exercised in such areas should thunderstorm activity initiate nearby. Finally,
as monsoon moisture declines, any continued convective activity may result in
relatively little rainfall while still being capable of generating lightning,
which can pose a risk of wildfire initiation.
Toward the middle of week-2, troughing along the West Coast is favored to
retreat with rising heights across the West tied to expansion of the ridging
over the south-central CONUS. This evolution would decrease the moisture
advection into the West, and also promote an increase in above-normal
temperatures and possibly extreme heat across portions of the Interior West
where the GEFS PET depicts increasing coverage of probabilities greater than 20
percent for maximum temperatures to exceed the 85th climatological percentile.
Daily maximum temperatures from multiple model ensembles exceed 105F across the
Sonoran and Mojave deserts through the middle of week-2, after which indicated
maximum temperatures moderate somewhat. Increased humidity from the monsoon is
likely to result in relatively muggy conditions for the area. Therefore a
slight risk of extreme heat is posted for much of the Desert Southwest and
extending into central New Mexico, valid Aug 22-26.
A Rapid Onset Drought (ROD) risk remains designated across portions of the
Central and Southern Plains and Middle and Lower Mississippi Valley. 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
$$
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts
www.nws.noaa.gov
