811
FXUS21 KWNC 311738
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 31 2025

SYNOPSIS: Late in week-1 into the outset of week-2, dynamical models are in
good agreement regarding a robust area of mid-level low pressure developing
across the Great Lakes and Northeast. This feature is likely to bring weather
more typical of early Fall. As surface high pressure builds over the Northeast,
enhanced easterly flow is favored across the Southeast, 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.

HAZARDS

Slight risk of heavy precipitation across parts of the Desert Southwest,
Mon-Fri, Sep 8-12.

Slight risk of heavy precipitation across Florida, the eastern Gulf Coast, and
coastal portions of the Carolinas and Southeast, Mon-Fri, Sep 8-12.

Slight risk of high winds across Florida, the eastern Gulf Coast, and coastal
portions of the Carolinas and Southeast,  Mon-Wed, Sep 8-10.

Slight risk of much below normal temperatures across portions of the Upper
Mississippi Valley and Great Lakes, Mon, Sep 8.

DETAILED SUMMARY

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

FOR MONDAY SEPTEMBER 08 - SUNDAY SEPTEMBER 14: Late in week-1, a highly
amplified 500-hPa height pattern is predicted across North America, with strong
ridging across the Gulf of Alaska and western Canada, and troughing downstream
over the eastern U.S. These features are forecast to persist into the beginning
of week-2 before slowly weakening. The ridging over western North America
favors anomalous warmth across the Northwest, with extreme heat concerns during
the week-1 period. While above-normal temperatures are still likely during
week-2, the signals for extreme heat diminish compared to the week-1 timeframe.
Nonetheless, anticipated hot and dry conditions may lead to enhanced wildfire
risk across interior portions of the Northwest and northern California.



Downstream over the north-central and northeastern CONUS, the amplified trough
moving across the region will bring a noticeable cool-down after frontal
passage and associated precipitation which is likely to move through prior to
week-2. Behind this front unseasonably cold air temperatures are depicted by
model ensembles, with potential for frost conditions lingering into week-2. In
particular, the ECENS PET depicts probabilities exceeding 20 percent for
minimum temperatures in the lowest 15th climatological percentile and below 40
deg F over much of the Upper Mississippi Valley, Great Lakes, and into parts of
the Interior Northeast. The GEFS PET is not quite as bullish as the ECENS but
still indicates at least a 20% chance of minimum temperatures below 40F at the
outset of week-2. Todays forecast extends the slight risk of much below normal
temperatures over portions of the Upper Mississippi Valley and Great Lakes into
Sep 8 given good agreement among the tools with regard to the potential frost
risk. While it is uncertain the extent of areas that will drop below 40 deg F,
any isolated areas that dip into the 30s deg F could be at risk for frost over
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, affected
areas are generally sparsely populated or at higher elevations where such
conditions would have menial 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. Todays
forecast removes the Texas coast from the existing slight risk of heavy
precipitation along the Gulf Coast. Ensemble solutions are in much better
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 weeks end. 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 8-12. 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 8-10.



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 more 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 expanded further into northern Arizona and northwestern New
Mexico, and extended to cover Sep 8-12.

FORECASTER: Danny Barandiaran

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