316
FXUS21 KWNC 011836
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 01 2025

SYNOPSIS: At the outset of week-2 surface high pressure builds over the
Northeast, enhancing easterly flow across the Southeast and southerly flow over
the Great Plains, with a wavering frontal system contributing to periods of
unsettled weather across the Gulf and Southeast Coasts including Florida. Over
the Southwest, potential tropical cyclone development west of Mexico could
enhance tropical moisture, increasing the potential for episodes of locally
heavy precipitation for the region through the middle of the period. Surface
low pressure over the Desert Southwest coupled with high pressure over the
Rockies brings the potential for high winds across much of the Great Basin.

HAZARDS

Slight risk of heavy precipitation across parts of the Desert Southwest,
Tue-Thu, Sep 9-11.

Slight risk of heavy precipitation across Florida, the eastern Gulf Coast, and
coastal portions of the Carolinas and Southeast, Tue-Sat, Sep 9-13.

Slight risk of high winds across Florida, the eastern Gulf Coast, and coastal
portions of the Carolinas and Southeast,  Tue-Thu, Sep 9-11.

Slight risk of high winds over portions of the Southern and Central Plains,
Tue-Fri, Sep 9-12.

Slight risk of high winds over much of the Great Basin and portions of the
Desert Southwest, Tue-Mon, Sep 9-15.

DETAILED SUMMARY

FOR THURSDAY SEPTEMBER 04 - MONDAY SEPTEMBER 08:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR TUESDAY SEPTEMBER 09 - MONDAY SEPTEMBER 15: Todays model ensembles
continue to depict a strong mid-level trough over the north-central and
northeastern Contiguous U.S. (CONUS) during week-1, bringing a noticeable
cool-down after frontal passage and associated precipitation. By the outset of
week-2 this trough is favored to deamplify significantly and move northward,
while surface high pressure settles into the Northeast U.S., bringing
unseasonably cold air temperatures to the northeastern CONUS, with potential
for frost conditions lingering into week-2. Most of the coldest temperatures
are now expected in week-1 so no associated hazard is posted, however isolated
frost conditions may remain, posing a risk for susceptible vegetation.
Nighttime temperatures are also favored to be unseasonably cool for much of New
England. Isolated areas of frost and even freezing conditions in higher
elevations are possible early in week-2, however affected areas are generally
sparsely populated or at higher elevations where such conditions would have
minimal impact, therefore no associated hazard is posted at this time.



The aforementioned front is forecast to become quasi-stationary across the Gulf
Coast and Southeast during week-2, with surface high pressure over the
Northeast leading to enhanced easterly flow across the Southeast. As a result,
unsettled weather is likely over these areas throughout the period, in the form
of episodic heavy precipitation and potentially elevated wind speeds.
Uncalibrated guidance from the 0z ECENS and GEFS generally depicts the heaviest
precipitation amounts just offshore, but it would not take much of a shift to
bring these higher totals to the coast. The GEFS and ECENS PETs depict at least
a 20 percent chance of 3-day precipitation totals exceeding the 85th percentile
and 1-inch along the Gulf and Southeast coasts for much of week-2. Both
yesterday and todays model solutions have shown larger spread with regard to
rainfall totals for the Texas coast, potentially due to uncertainty with regard
to the robustness of the stationary boundary along its western margin. Ensemble
solutions are in reasonable agreement with regard to the duration of this
event, depicting a gradual reduction of enhanced precipitation associated with
this system over the course of the week, likely falling below hazardous
thresholds by the end of week-2. Therefore the slight risk of heavy
precipitation is posted for the Gulf Coast east of the Mississippi Delta, all
of Florida, and up the Georgia and Carolina coasts for Sep 9-13. Additionally,
the ECENS and GEFS 10m wind speed forecasts indicate enhanced winds initially
developing associated with this squally weather, with episodic enhanced winds
of 20mph or more along the coast, although models generally indicate that these
stronger winds are not likely to continue as long as the enhanced
precipitation. Therefore the slight risk of high winds for the Gulf coast from
the Mississippi Delta east across Florida and up the Atlantic coast to the
Outer Banks is updated today to cover only Sep 9-11.



Strong return flow around the western edge of the surface high pressure over
the eastern CONUS is favored to enhance winds over the Great Plains. Ensemble
mean surface wind speed periodically approaches 20mph along the lee of the
Rockies in both the GEFS and ECENS uncalibrated output, while the ECENS PET
indicates at least a 20% chance of 3-day maximum wind speeds to exceed the 85th
climatological percentile over the Great Plains throughout the week. Based on
the best consensus between guidance a slight risk of high winds is posted for
western portions of the Southern and Central Plains for Sep 9-12.



Tropical cyclone development is likely across the East Pacific during the next
week, with the potential of at least one system to track northwestward, with
the ECENS tracking closer to Baja California and the GEFS farther offshore. A
more northerly component of the track is likely to enhance moisture over parts
of the Southwest leading to elevated chances of heavy precipitation. Todays
ensemble solutions are slightly less bullish with regard to both the duration
of tropical moisture advection into the Desert Southwest as well as the
potential precipitation totals resulting, so the slight risk of locally heavy
precipitation is shortened to cover Sep 9-11.



With or without associated tropical moisture, models depict a robust thermal
low over the Desert Southwest as well as surface high pressure over the
Rockies, setting up a steep pressure gradient resulting in enhanced winds over
the Great Basin. This is well-supported by the ECENS PET which indicates at
least a 20% chance of 3-day wind speeds to exceed the 85th percentile
throughout the week, and by uncalibrated surface wind ensemble means from the
ECENS and GEFS, which both indicate afternoon winds reaching or exceeding
20mph. A slight risk of high winds is posted for much of the Great Basin and
Northern Rockies for all of week-2. While temperatures are favored to be near-
to below-normal for the region, wildfire hazards are likely to be enhanced by
these windy conditions.

FORECASTER: Danny Barandiaran

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