032
FXUS21 KWNC 311901
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 31 2025

SYNOPSIS: Mid-level high pressure is forecast to expand across the Four Corners
and southwestern contiguous U.S. (CONUS) late in week-1 into early week-2. This
favors an increased risk for extreme heat extending from the California Central
Valley eastward to the south-central CONUS, with record-breaking high
temperatures possible, particularly over the Southwest. Elevated wind speeds
remain possible along portions of the West Coast and over parts of the Interior
West, High Plains, and the Rio Grande Valley, which when combined with the hot,
dry conditions forecast, may enhance the wildfire threat over some of these
areas. No hazardous areas of precipitation are indicated across the domain
during week-2, although enhanced onshore flow favors unsettled weather across
southeastern Alaska.

HAZARDS

High risk of extreme heat for portions of the Desert Southwest, Fri, Aug 8.

Moderate risk for extreme heat for southern portions of the California Central
Valley, Desert Southwest, Southern Rockies, Central and Southern Plains, and
Middle and Lower Mississippi Valley, Fri-Sun, Aug 8-10.

Slight risk of extreme heat for much of the Southwest, Central and Southern
Plains, and Middle and Lower Mississippi Valley, Fri-Thu, Aug 8-14.

Slight risk of episodic high winds for coastal California from Point Conception
to Cape Mendocino, Fri-Sat, Aug 8-9.

Slight risk of episodic high winds for much of the Great Basin as well as
portions of the Desert Southwest, Central and Northern Rockies, and Northern
High Plains, Fri-Sat, Aug 8-9.

Slight risk of episodic high winds for much of the Central and Southern High
Plains, Fri-Tue, Aug 8-12.

Rapid onset drought risk across southwestern Oklahoma.

DETAILED SUMMARY

FOR SUNDAY AUGUST 03 - THURSDAY AUGUST 07:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY AUGUST 08 - THURSDAY AUGUST 14: A highly anomalous ridge (597-600
dm) is forecast to build over the Four Corners region of the U.S. late in
week-1 and persist into the outset of week-2 before weakening. There is
increasing confidence for a significant extreme heat event across portions of
the Southwest, and expanding both westward and eastward to include the
California Central Valley and the south-central CONUS. The uncalibrated 0z
ECENS and GEFS depict maximum temperatures possibly reaching 115-120 deg F
across portions of the Desert Southwest on day-8 (Aug 8), which is quite
impressive considering the lead. The GEFS Probabilistic Extremes Tool (PET)
also depicts at least a 60 percent chance maximum temperatures exceed the 85th
climatological percentile over the Four Corners, with 40 percent or greater
probabilities extending east across the Southern Plains and Mississippi Valley
on day-8 (Aug 8). The ECENS PET shows generally slightly weaker probabilities
of 50-60 percent indicated over the Desert Southwest, but also extended west to
include southern portions of the California Central Valley. As the period
progresses, probabilities in both PETs gradually decrease. Additionally the
skill-weighted calibrated heat risk tool depicts at least a 60 percent chance
of temperatures exceeding the 90th climatological percentile during week-2 over
the Southwest.



Given these strong heat signals, especially early in the period, a high risk
for extreme heat is posted across the Desert Southwest on day-8 (Aug 8)
corresponding with where the highest temperatures are predicted (greater than
115 deg F). The moderate risk continues through day-10 (Aug 10) and includes
the southern half of the California Central Valley where temperatures in the
105-110 deg F range are possible, the Desert Southwest and much of New Mexico
where the National Blend of Models depicts record high temperatures, and the
south-central CONUS where triple digit temperatures or heat indices are
depicted in the model guidance. There was some consideration for a high risk
across the California Central Valley based on model temperatures. However,
persistent mid-level troughing off the coast has worked to keep conditions
slightly cooler compared to forecast temperatures thus supporting only having a
moderate risk. Humidity is likely to be more of a factor across the eastern
Great Plains and Mississippi Valley, with heat risk guidance depicting 60
percent or greater probabilities for heat indices exceeding 105 deg F. Further
to the west across western Texas and the High Plains, temperatures above 100
deg F are possible, although lower humidity values may decrease the extreme
heat risk a bit, particularly across southwestern Texas. A slight risk for
extreme heat continues for all of week-2 across the Southwest eastward to the
Central and Southern Plains and Middle and Lower Mississippi Valley. Positive
mid-level height anomalies over eastern North America favor warm temperatures
returning to portions of the northeastern CONUS by the second half of week-2.
However, temperatures in the uncalibrated models are marginal in terms of
reaching extreme heat thresholds and the signal may be more tied to anomalously
warm overnight temperatures. Trends will continue to be monitored for the
possible addition of a slight risk of extreme heat in future outlooks across
the region.



At the outset of week-2 a weakening trough over the Northern Tier is favored to
enhance daytime winds for much of the interior western CONUS. A slight risk of
high winds is posted for much of the Desert Southwest, Great Basin, Central and
Northern Rockies, and Northern High Plains for Aug 8-9, where the ECENS PET
indicates at least a 20 percent chance of 3-day maximum winds exceeding the
85th climatological percentile. The GEFS PET is less bullish, confining
enhanced winds primarily to the Great Basin, but uncalibrated probabilistic
guidance from both model ensembles indicate very high likelihood of daytime
winds exceeding 20-mph for the same period of time, after which this threshold
becomes less likely.



The summer subtropical surface high over the North Pacific has been quite
strong recently, which has had the potential of enhancing coastal winds typical
for this time of year. Model guidance indicates that this enhancement is likely
early in the period before the ridging over the Southwest becomes more
dominant. The GEFS and ECENS PETs both indicate probabilities of at least 60
percent for winds near the California coast exceeding 25-mph early in the
period, supporting a slight risk of high winds for coastal portions of
California from Point Conception to Cape Mendocino for Aug 8-9.



Models also depict enhanced easterly winds over the western Gulf and extending
into southern Texas and the High Plains throughout the forecast period,
associated with tropical flow and enhanced by surface low pressure over the
Great Plains. This enhancement is greatest at the outset of week-2 where
ensemble mean wind speeds are forecast to exceed 20-mph for much of South
Texas. Troughing weakens quickly so enhanced surface winds diminish somewhat,
but ensemble mean daily maximum winds remain elevated through Aug 12.
Therefore, a slight risk of episodic high winds is posted for much of the
Texas-Mexico border and extending through the central and southern High Plains
for Aug 8-12. The region is also favored for below-normal precipitation and
above-normal temperatures, the combination of which creates a very favorable
environment for initiation and rapid growth of wildfires. Rapid onset drought
risk is indicated across portions of southwestern Oklahoma due to relatively
lower 30-day precipitation totals compared to surrounding areas.



Enhanced onshore flow is forecast across southeastern Alaska during week-2
leading to increased precipitation and gusty winds, although hazardous
thresholds are not expected to be reached. However, some concern exists for
mudslides across more vulnerable areas.

FORECASTER: Thomas Collow

$$