513
FXUS21 KWNC 241803
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 24 2025

SYNOPSIS: A broad area of mid-level low pressure is forecast over the eastern
and central contiguous U.S. (CONUS) to start September. During much of the
first week of September, a stationary front is forecast to extend from near the
Gulf Coast westward to New Mexico. There is an increasing chance of a tropical
cyclone (TC) to develop in the East Pacific at the beginning of September with
a subsequent northwest track towards the Baja Peninsula which could eventually
lead to a heavy rainfall risk for the Desert Southwest. The peak of the
Atlantic hurricane season is in early September and the Atlantic basin will be
closely monitored for tropical cyclone development.

HAZARDS

Slight risk of heavy precipitation for parts of Florida and the coastal
Southeast, Mon-Tue, Sep 1-2.

Slight risk of high winds for the Outer Banks of North Carolina, Mon-Tue, Sep
1-2.

Slight risk of heavy precipitation for the western Gulf Coast, Wed-Sat, Sep
3-6.

Slight risk of heavy precipitation for parts of the Desert Southwest, Fri-Sun,
Sep 5-7.

DETAILED SUMMARY

FOR WEDNESDAY AUGUST 27 - SUNDAY AUGUST 31:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY SEPTEMBER 01 - SUNDAY SEPTEMBER 07: Prior to the start of week-2, a
highly amplified 500-hPa trough over eastern North America is forecast to drive
a cold front well southward to the Florida Peninsula. Once this front becomes
stationary by the beginning of September, it could provide a focus for heavier
rainfall across parts of Florida. Several of the ECENS and GEFS ensemble
members favor a wave of low pressure developing along the stationary front with
a track near the coastal Southeast. Based on 24-hour precipitation amounts from
the ensemble mean solutions and the elevated chance of a wave of low pressure,
a slight risk of heavy precipitation is posted for parts of Florida and the
coastal Southeast, September 1-2. This heavy rainfall risk is related more to
the synoptic scale than the typical sea breeze convection at this time of year.
Although the ensemble members only favor a relatively weak surface low forming
if at all, the pressure gradient between this potential low and a strong
surface high across New England and the Canadian Maritimes results in a slight
risk of high winds for the Outer Banks on September 1 and 2.



The GEFS and ECENS depict a front slowly shifting back northward closer or
inland of the western Gulf Coast early in week-2. Beginning on September 3rd
through the 6th, a slight risk of heavy precipitation is designated for the
Louisiana and Texas Gulf Coast. This heavy precipitation hazard is consistent
with the ECMWF Probabilistic Extremes Tool (PET) and 24-hour precipitation
amounts from the GEFS and ECENS models. Although there does not appear to be
much model support for tropical cyclone (TC) development along the front, this
will be monitored in the coming days. The ECMWF PET would also favor
designating a slight risk of heavy precipitation across the Upper Rio Grande
Valley and eastern New Mexico which may be on the tail end of a front. However,
the much drier GEFS model solution precludes any hazard risk for those areas.



As of 11am PDT on August 24, the National Hurricane Center is monitoring a
broad area of low pressure several hundred miles offshore of southwestern
Mexico. The NHC states that a TC is likely (90 percent chance in the next 2
days) to form in the East Pacific. Following this potential TC, the ECENS and
GEFS are in good agreement that one or two additional TCs form in the East
Pacific during the next week to ten days. Many of the ECENS and GEFS ensemble
members favor a TC developing close to coastal southwestern Mexico and tracking
northwest towards the Baja Peninsula or southern Gulf of California during
early September. This predicted TC track would increase the chance for a surge
of enhanced low to mid-level moisture northward to the Desert Southwest. Given
the ensemble model support and consistent with the ECMWF PET, a slight risk of
heavy precipitation is posted for the Desert Southwest from September 5-7.



Although above-normal temperatures are favored across the Pacific Northwest and
Northern Intermountain West, hazardous heat becomes much less likely by early
September. The most anomalous warmth is expected across the interior areas of
Oregon and Washington along with southwestern Idaho where 7-day temperatures
are forecast to average near 10 degrees F above normal according to the ECENS.
However, even on the predicted warmest days early in week-2, maximum
temperatures are forecast to be in the lower 90s in southeastern Washington and
the Snake River Valley of southern Idaho. Therefore, a slight risk of extreme
heat is not posted.



Early week-2, an amplified 500-hPa trough is forecast over the Aleutians, with
enhanced onshore flow across coastal southern Alaska. Multi-day precipitation
amounts are unlikely to reach hazardous thresholds.

FORECASTER: Brad Pugh

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