249
FXUS21 KWNC 231818
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 23 2025

SYNOPSIS: At the beginning of week-2, a frontal system is favored to move
across the southeastern and south-central Contiguous U.S. (CONUS), helping to
focus potentially hazardous precipitation across this region. An area of
surface low pressure may form along the front near the Southeast coast,
increasing regional precipitation amounts and winds. Surface low pressure over
the Lower Colorado Basin combined with surface high pressure over the Rocky
Mountains results in the potential for episodic high winds over the Great Basin.

HAZARDS

Slight risk of heavy precipitation for the vicinity of the Lower Mississippi
Valley, Sun, Aug 31.

Slight risk of heavy precipitation for portions of the Southeast and Gulf
coasts, Sun-Thu, Aug 31-Sep 4.

Slight risk of high winds from the central Gulf coast across much of Florida
and parts of the Southeast coast, Sun-Thu, Aug 31-Sep 4.

Slight risk of episodic high winds for California, much of the Great Basin and
Desert Southwest, Sun-Thu, Aug 31-Sep 4.

DETAILED SUMMARY

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

FOR SUNDAY AUGUST 31 - SATURDAY SEPTEMBER 06: Model ensembles indicate a fairly
strong mid-level trough over the northeastern CONUS early in week-2, which
model solutions gradually flatten out by the end of the forecast period. A
frontal system associated with this trough is predicted from off the Southeast
coast across Florida, the northern and central Gulf of America, and the far
southern Great Plains. A weakening wave of low pressure along the western end
of the front may contribute towards a slight chance of heavy precipitation on
August 31st in the vicinity of the Lower Mississippi Valley. This means the
precipitation amounts are expected to exceed the 85th historical percentile and
at least 1-inch. A slight risk of heavy precipitation is also designated
farther east, from the central Gulf coast across Florida to near/along the
Southeast coast, Aug 31-Sep 4. Uncalibrated ECENS and GEFS precipitation
amounts exceed 2 inches over portions of the Florida peninsula in the proximity
of a stationary front. Daily surface forecasts of the GEFS and ECENS indicate a
surface low may spin up on the front along the Southeast coast early in week-2,
with the GEFS solution favoring a westward spreading precipitation shield over
the Southeast, while the ECENS favors most of the precipitation remaining
offshore. Though this outlook leans toward the ECENS guidance, this scenario
will be closely monitored as we approach the climatological peak of the
Atlantic hurricane season, and may need to be adjusted accordingly. A slight
risk of high winds (greater than the 85th percentile and 20 mph) is posted from
the central Gulf coast across much of Florida and parts of the Southeast coast,
Aug 31-Sep 4, associated with the expected development of a surface low in the
region. Some portions of the Southeast U.S. have recently received abundant
antecedent rainfall, setting the stage for potential localized flooding or
flash flooding as a result of additional rainfall, as well as the potential for
coastal flooding from storm surge should a tropical cyclone spin up. Model
agreement is unfortunately low regarding the details of this potential tropical
activity, precluding better detail regarding timing and regional effects, so no
flooding hazards are posted at this time but the situation will be closely
monitored in the coming days.



The continued presence of a thermal low over the Desert Southwest paired with
high pressure over the Rockies sets up an enhanced pressure gradient and the
potential for high winds over much of the Great Basin (Aug 31-Sep 4).
California is included in this wind hazard, though it is largely due to a
mid-level trough that is forecast to be near the West Coast, and the eastward
ejection of shortwave energy. Diurnal heating and resultant mixing may help to
bring some of the stronger winds aloft down to the surface. This wind hazard is
well indicated by both the ECENS and GEFS Probabilistic Extremes Tools (PETs)
which indicate at least a 20% chance of 3-day maximum wind speeds exceeding the
85th climatological percentile and at least 20 mph over much of the region for
most of week-2. Given numerous active wildfires already in progress across this
area, enhanced wind speeds may augment current wildfire activity or help in the
initiation of new fires. This is noteworthy since September (and October) are
often associated with a secondary peak in temperatures in California, and
usually signals a ramp-up in downslope wind events.



Across southern Alaska, uncalibrated GEFS and ECENS precipitation guidance
predicts at least a 20 percent chance precipitation amounts will reach/exceed 2
inches from about the Kenai Peninsula to the southern tip of the Alaska
Panhandle. This is related to increased onshore flow. No precipitation hazard
is posted for this region today, but this potential will be reassessed tomorrow.

FORECASTER: Anthony Artusa

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