672
FXUS21 KWNC 221904
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT August 22 2025

SYNOPSIS: A frontal system is favored to move over the central and eastern
CONUS at the outset of the forecast period, resulting in potentially heavy
precipitation for portions of the Great Plains and Mississippi Valley early in
week-2. Disturbed weather and a possible surface low pressure to form off the
Carolina coast results in enhanced precipitation and high winds, some of which
may affect coastal portions of the Southeast U.S. 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 portions of the Southern and Central
Plains, and the Lower and Middle Mississippi Valley, Sat-Sun, Aug 30-31.

Slight risk of heavy precipitation for portions of the Southeast U.S. and
Mid-Atlantic, Sat-Wed, Aug 30-Sep 3.

Slight risk of high winds for coastal areas from the Florida-Georgia border
north to and including the Delmarva Peninsula, Sat-Wed, Aug 30-Sep 3.

Slight risk of episodic high winds for much of the Great Basin and Desert
Southwest, Sat-Wed, Aug 30-Sep 3.

DETAILED SUMMARY

FOR MONDAY AUGUST 25 - FRIDAY AUGUST 29:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR SATURDAY AUGUST 30 - FRIDAY SEPTEMBER 05: Model ensembles indicate a fairly
strong mid-level trough over the northeastern U.S. early in week-2, which model
solutions flatten out quickly as the forecast period progresses. A frontal
system associated with this trough is favored to bring potentially heavy
precipitation to the midsection of the Lower 48. Much of the potential for
enhanced precipitation is during the week-1 period but has the potential to
linger into the beginning of week-2. A slight risk of heavy precipitation is
posted for portions of the Southern Plains, Lower Mississippi Valley, Tennessee
Valley, and Southeast U.S. for Aug 30-31, when probabilistic output from the
GEFS and ECMWF both indicate at least a 20% chance of daily precipitation
accumulations to exceed 0.5 inches. While the ECWMF favors enhanced
precipitation to continue well into week-2, there is insufficient evidence to
extend this hazard into September.



Lingering instability from the frontal system mentioned above along with
abundant tropical moisture leads to the potential for enhanced precipitation
and high winds along the southeastern U.S. coastline. Model solutions from the
ECMWF and GEFS both indicate the potential for a surface low to spin up off the
Carolina coast and possibly become a tropical cyclone (TC) during the week-2
period, and at the very minimum enhancing precipitation along the southeastern
coast. At this time a slight risk of heavy precipitation is posted for Aug
30-Sep 3 for much of Florida, and coastal portions of the Southeast U.S. and
Mid-Atlantic, and a slight risk of high winds is posted for coastal areas from
the Florida-Georgia border north to Delaware Bay for the same days. 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 TC 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 a tight pressure gradient and the
potential for high winds over the Great Basin. This is well-indicated by both
the ECMWF 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 20mph over the Great Basin for most of week-2. A slight
risk of high winds is posted for much of the Mojave and Sonoran Deserts, the
Great Basin and Snake River Valley, and portions of the Northern Rockies for
Aug 30-Sep 3. Although raw output from the GEFS indicate the potential for
these enhanced winds to continue throughout week-2, in general model solutions
diverge later in the forecast period reducing confidence in this result. Given
numerous active wildfires in the region and the potential for enhanced winds to
increase the risk of initiation and spread of wildfires.

FORECASTER: Danny Barandiaran

$$