403
FXUS21 KWNC 291726
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 29 2026

SYNOPSIS: Broad mid-level ridging is forecast to persist across the
south-central contiguous U.S. (CONUS) into week-2 favoring a continuation of
anomalous warmth and extreme heat centered across the Central and Southern
Plains into the Middle and Lower Mississippi Valley. Enhanced moisture,
potentially associated with the remnants of Tropical Storm Dolly, may bring
unsettled weather to portions of Florida and the Southeast early in the period.
Mid-level low pressure forecast across the northwestern CONUS early in the
period favors early season frosts or freezes, particularly across higher
elevations. The abnormally hot and dry conditions over the past few weeks are
expected to continue through much of week-2, supporting a Rapid Onset Drought
(ROD) risk for portions of the Central and Southern Plains and the Middle and
Lower Mississippi Valley.

HAZARDS

Moderate risk of extreme heat for parts of the Central and Southern Plains,
Middle and Lower Mississippi Valley, western portions of the Tennessee and Ohio
Valleys, and the Southeast, Sun-Tue, Sep 6-8.

Slight risk of extreme heat for parts of the Desert Southwest, Great Plains,
Mississippi, Ohio, and Tennessee Valleys, Southeast, Sun-Thu, Sep 6-10.

Slight risk of much below normal temperatures for parts of the northern Great
Basin, Northern Rockies, and Northern High Plains, Sun, Sep 6.

Slight risk of heavy precipitation for parts of the Southeast, Sun-Mon, Sep 6-7.

Rapid Onset Drought (ROD) risk for portions of the Central and Southern Plains
and the Middle and Lower Mississippi Valley.

DETAILED SUMMARY

FOR TUESDAY SEPTEMBER 01 - SATURDAY SEPTEMBER 05:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SUNDAY SEPTEMBER 06 - SATURDAY SEPTEMBER 12: The 0z ECMWF, GEFS, and
Canadian ensembles are in good agreement regarding mid-level ridging across the
south-central CONUS at the start of week-2, with the ECMWF ensemble depicting a
594-dm ridge axis persisting through day-10, but with more of a retrogression
into the High Plains compared to the other guidance. This evolution supports a
continuation of anomalously warm temperatures (upwards of +10 deg F above
normal) across the Central and Southern Plains and adjacent areas of the
Mississippi Valley. The GEFS and ECMWF Probabilistic Extremes Tools (PETs)
depict at least a 40 percent chance of maximum temperatures exceeding the 90th
climatological percentile early in the period, with a very strong signal also
being depicted in the GEFS-ECMWF skill-weighted calibrated heat risk guidance.
Actual temperatures in the upper 90s deg F to 100s deg F are likely with heat
index values near 110 deg F in the more humid areas of eastern Texas and the
Lower Mississippi Valley and 105 deg F farther north. As a result of the more
amplified ECMWF ensemble, the moderate risk for extreme heat is now extended
through Sep 8 across parts of the Central and Southern Plains, Middle and Lower
Mississippi Valley, western portions of the Tennessee and Ohio Valleys, and the
Southeast. The slight risk continues through Sep 10 and extends throughout much
of the Midwest, and also into the Southeast. The slight risk is extended into
the Desert Southwest where retrogression of the mid-level ridge may result in
temperatures greater than 105 deg F. While positive 500-hPa height anomalies
are forecast throughout the period, the declining temperature climatology and
shortening daylight hours reduce confidence regarding extreme heat heading into
mid-September.



The continued extreme heat risks during week-2 are likely being reinforced by
feedback processes associated with rapidly drying soils and drought within many
of the highlighted regions. The hot and dry conditions favored are also
expected to elevate the risk of fire weather conditions during the period. In
addition, a Rapid Onset Drought (ROD) risk is designated across portions of the
Central and Southern Plains and Middle and Lower Mississippi Valley. This area
has registered 30- to 45-day precipitation deficits greater than 2 inches below
normal and/or under half of normal, with less than an inch expected during the
next two weeks.



Amplified ridging forecast across the Gulf of Alaska results in downstream
troughing developing over the northwestern CONUS late in week-1. This favors
enhanced onshore flow and moisture advection leading to above-normal
precipitation over much of the West. The ECMWF and Canadian ensembles are
quicker to weaken this feature early in week-2 compared to the GEFS, with a
faster retrogression of the upstream ridge leading to rising heights over the
West.  While precipitation amounts are unlikely to reach hazards thresholds
during week-2, cold air advection is forecast across portions of the Northwest,
with both ECMWF and GEFS ensembles showing increased chances for nighttime
minimum temperatures falling below 40 deg F (32 deg F in the higher elevations)
supportive of the first frost and/or freezes. While the strongest signals are
beginning to decline and time off into the late week-1 period, a slight risk
for much below normal temperatures remains posted on day-8 (Sep 6) across parts
of the northern Great Basin, Northern Rockies, and Northern High Plains,
consistent with where the ECMWF PET still depicts at least a 20 percent chance
minimum temperatures fall below the 15th climatological percentile. Even if any
frost and/or freezes do not occur, the prospect of anomalously cold air is
expected to alleviate fire weather conditions, as this part of the country has
been embattled by ample wildfire activity this summer.



Across the eastern and central Pacific, there has been a pronounced uptick in
tropical activity during the past week. Tropical Storms Karina and Lowell are
located near 120 deg W and 135 deg W respectively. The National Hurricane
Center (NHC) forecasts Karina to strengthen into a major hurricane as it tracks
west-northwestward. Karina along with a potential additional area highlighted
with a high chance for tropical cyclone development in the same area may lead
to enhanced moisture advection across the southwestern U.S. Both of these
systems are forecast to be moving farther away from the U.S. by the start of
week-2. However, the ECMWF ensembles depict another system potentially
developing offshore Mexico with a similar track which will need to be monitored
as it could trigger a renewed Gulf surge event in mid to late week-2.



Tropical Storm Lowell is forecast to strengthen into a hurricane as it moves
westward across the Pacific. This system will need to be monitored as some GEFS
and ECMWF ensemble members turn the system more north toward the Hawaiian
Islands early in week-2. Although there is ample uncertainty associated with
this disturbance, heavy precipitation and other adverse impacts to Hawaii
cannot be ruled out during week-2, with both the GEFS and ECMWF PETS depicting
at least a 20 percent chance of 3-day precipitation values exceeding the 85th
climatological percentile across the state.



Across the Atlantic, Tropical Storm Dolly has opened up into a wave. There is
some potential for regeneration if the remnants of this system make it into the
western Atlantic where there is notably less wind shear, although NHC gives
this low odds in the next 7 days (10 percent). The timing and exact location
are uncertain, but some individual GEFS and ECMWF ensemble members depict
surface low pressure in the vicinity of the western Atlantic, Southeast U.S.,
or eastern Gulf of America late in week-1 into early week-2. While unlikely to
be a significant system, periods of heavy precipitation may impact portions of
Florida into the Southeast, supporting a slight risk of heavy precipitation Sep
6-7.



Enhanced onshore flow may bring periods of heavy precipitation and gusty winds
across southern Alaska late in week-1 into the start of week-2, although tools
do not indicate hazards thresholds being reached. Snow cannot be ruled out
across portions of the Brooks Range and the higher elevations of southeastern
Alaska.

FORECASTER: Thomas Collow

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