745
FXUS21 KWNC 071809
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 07 2026

SYNOPSIS: Mid-level high pressure is favored to rebuild over the south-central
and southeastern contiguous U.S. (CONUS) supporting a continuation of extreme
heat risks from the Southern Plains to the Southeast early in week-2. Enhanced
tropospheric moisture is favored to overspread much of the Interior West and
eastward towards the Appalachians, bringing an increased risk of heavy
precipitation for much of central and southwestern CONUS. Antecedent dryness,
combined with little precipitation favored over the next two weeks supports a
Rapid Onset Drought (ROD) risk for portions of the Southern and Central Plains
and Lower Mississippi Valley.

HAZARDS

Moderate risk of extreme heat for portions of the Southern Plains, Lower
Mississippi Valley, and Southeast, Sat-Mon, Aug 15-17.

Slight risk of extreme heat for much of the south-central and southeastern
CONUS, Sat-Fri, Aug 15-21.

Slight risk of heavy precipitation for portions of the Desert Southwest,
southern Great Basin, Central and Southern Rockies, Great Plains, and
Mississippi and Ohio Valleys, Sat-Mon, Aug 15-17.

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

DETAILED SUMMARY

FOR MONDAY AUGUST 10 - FRIDAY AUGUST 14:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SATURDAY AUGUST 15 - FRIDAY AUGUST 21: By late next week and into the
following weekend, there is good agreement in the dynamical models favoring the
return of rising 500-hPa heights over the south-central and southeastern CONUS
as troughing over the Northeast weakens and lifts out by the outset of week-2.
While temperature tools show a good amount of cooler temperatures overspreading
much of the Midwest and eastern U.S. tied to a more amplified solution of this
troughing feature late in week-1, the rebuilding subtropical ridge continues to
support extreme heat risks mainly from the Southern Plains eastward to the
Southeast. With more troughing favored off of the West Coast, and the mean
ridge center displaced to the east of the Rockies early in week-2, much of the
monsoonal moisture supply is expected to ease into parts of the Desert
Southwest and lower Four Corners. However, residual monsoonal moisture, as well
as added moisture from the Pacific looks to overspread the Interior West and
into the portions of the Midwest, where there continues to an increased risk of
heavy precipitation along the northern periphery of the anomalous ridging
favored.



Later in week-2, there is increased outlook uncertainty due to discrepancies in
the evolving mid-level pattern among the models. The GEFS points to a
retrogression of the subtropical ridge, with more of a linkage to an amplified
ridge that is favored to remain established over the higher latitudes of
western Canada. This results in the development of full latitude ridging in the
GEFS supportive of an increasing risk of extreme heat returning to portions of
the Interior West and High Plains, with unseasonably colder air associated with
deeper troughing downstream over the northeastern CONUS. However, this
predicted pattern is at odds with the more stable ECMWF, which maintains a more
eastward solution of the subtropical ridge pattern, as well as more ridging
persisting over the northeastern Pacific to preclude the potential for full
latitude ridging from taking shape over western North America.



Based on the latest raw and calibrated temperature tools among the models, a
moderate risk of extreme heat is posted for the Southern Plains, Lower
Mississippi Valley, and the Southeast, and is extended through Aug 17. A
broader slight risk area of extreme heat also remains issued for much of the
south-central and southeastern U.S, where tools indicate lower probabilities
for heat exceeding hazardous thresholds, and is valid for all of week-2 based
on the favored persistence of at least 593-594 dm mean heights among the ECMWF,
Canadian, and GEFS-AI throughout the period. Due to the potential for cooler
air across the Central Plains and Middle Mississippi Valley later next week
resulting in lower heat index values, coverage has been slightly reduced along
the northern periphery of the moderate and slight risk areas. Within the
moderate risk area, Probabilistic Extreme Tools (PETs) maintain increased
chances of daytime temperatures exceeding the 85th percentile and calibrated
heat tools show 30-50% chances for either temperatures or heat index values
exceeding the 90th percentile. In addition, uncalibrated heat index guidance
shows values reaching 105-110 deg F where the National Blend of Models (NBM)
also shows a number of locations with nighttime lows nearing and/or breaking
daily records, where little overnight relief to daytime heat is expected.



Across the southwestern CONUS, analysis of precipitable water anomalies from
the ensembles show near to below normal values mainly over the Sonoran Desert,
suggestive of a reduction of monsoonal moisture advection. However, highly
anomalous precipitable water content is featured throughout the Interior West
and extending eastward towards the Appalachians associated with residual
monsoonal moisture with contributions of Pacific based moisture from  the
troughing favored offshore of the West Coast. As this enhanced tropospheric
moisture funnels eastward along the northern periphery of the subtropical
ridging over the south-central and southeastern CONUS, there remains an
increased risk of heavy precipitation with frontal forcing also in place across
the central CONUS early in week-2. Based on continued support in the PETs and
elevated probabilities of exceedance from the uncalibrated GEFS and ECMWF, a
slight risk of heavy precipitation remains posted over the Desert Southwest,
extending through the Rockies and eastward to the Appalachians for Aug 15-17.
Within the highlighted slight risk area, Mesoscale Convective System (MCS)
activity and localized flooding remain possible over the portions of the
Plains, Mississippi and Ohio Valleys. Despite the lowered moisture content
favored across the Desert Southwest, this region is still 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.



A Rapid Onset Drought (ROD) risk remains designated and includes parts of
Oklahoma, northeastern Texas eastward through northern Mississippi. 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 look to reinforce this risk later in
August.



Across the eastern Pacific, the National Hurricane Center (NHC) is monitoring a
pair of areas located near 140W and 110W with 30% and 20% chances of
development, respectively, during the next seven days (as of 11am PDT). For the
western watch area near 140W, both dynamical model and Google AI guidance have
been consistent favoring growing chances for development later next week, with
a mean low tracking near the Hawaiian Islands. While there continues to be much
uncertainty associated with this potential TC at this lead, tools continue to
indicate elevated chances for above-normal precipitation, with the ECMWF PET
maintaining 20-30% chances for 3-day amounts exceeding the 85th percentile. For
more info on this potential system, please refer to: https://www.nhc.noaa.gov/

FORECASTER: Nick Novella

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