541
FXUS21 KWNC 031812
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 03 2025

SYNOPSIS: At the outset of week-2, mid-level high pressure is forecast across
central North America favoring a pattern change with above-normal temperatures
returning across portions of the Great Plains and Midwest by the middle of the
period. Mid-level low pressure is forecast over the western third of the CONUS
favoring unsettled weather across the Pacific Northwest, and enhanced wind
speeds over much of the Southwest and extending through the Great Plains. A
stalled frontal boundary remains forecast along the East Coast and northern
Gulf of America resulting in increased likelihood for enhanced precipitation,
with uncertainty in regards to the inland extent of the heaviest precipitation.
Surface low pressure is forecast to bring increased chances of heavy
precipitation and elevated wind speeds to south-central coastal Alaska early in
the period.

HAZARDS

Slight risk of heavy precipitation across the Florida Peninsula extending
northward along the Southeast and Mid-Atlantic coasts, Thu-Sat, Sep 11-13.

Slight risk of high winds across Florida, the eastern Gulf Coast, and portions
of the East Coast, Thu-Mon, Sep 11-15.

Slight risk of high winds over much of the southwestern U.S. into the Rockies
and Great Plains, Thu-Sat, Sep 11-13.

Slight risk of high winds across coastal portions of southern Mainland Alaska,
Thu-Mon, Sep 11-15.

DETAILED SUMMARY

FOR SATURDAY SEPTEMBER 06 - WEDNESDAY SEPTEMBER 10:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY SEPTEMBER 11 - WEDNESDAY SEPTEMBER 17: Ridging and associated
positive 500-hPa height anomalies are forecast to expand across the
north-central U.S. early in week-2. This is likely to lead to a pattern change
with much warmer temperatures over portions of the Great Plains and Midwest
relative to earlier in week-1. The GEFS Probabilistic Extremes Tool (PET)
depicts probabilities of at least 20 percent for temperatures exceeding the
85th climatological percentile and 90 deg F extending north through portions of
the Central Plains, Middle Mississippi Valley, and Ohio Valley. However the
ECENS depicts a much weaker signal, and the uncalibrated 0z ECENS and GEFS
means generally depict temperatures in the 80s deg F over these areas. While
this is certainly warm by mid-September standards, these temperatures do not
necessitate an extreme heat risk thus no related hazard is posted.



Upstream of the aforementioned ridge, the 0z ECENS, GEFS, and CMCE depict
amplified troughing moving into the western CONUS. This feature is likely to
lead to some enhancement of precipitation, particularly across the Northwest
where the ECENS PET depicts high probabilities (greater than 60 percent) for
3-day precipitation exceeding the 85th climatological percentile. However,
probabilities in the GEFS PET are much lower (20-40 percent), and actual
24-hour precipitation amounts are forecast to be under a half-inch in the
uncalibrated versions of both models. Higher probabilities in the PETs are
likely tied to the lower precipitation climatology this time of year. While
unsettled weather is possible across the Northwest in association with the
trough, hazardous conditions are not expected, precluding a related
precipitation hazard. The trough may support elevated wind speeds throughout
much of the southwestern U.S. into the Great Plains. A slight risk of high
winds is posted over portions of the California Coast, Great Basin, Rockies,
and Great Plains, Sep 11-13, coinciding with the strongest signal in the ECENS
PET. Wildfire development and spread is the primary concern across the West due
to soil moisture values in the lowest 10th climatological percentile. The wind
threat is forecast to subside later in week-2 as the troughing weakens.



A stalled frontal boundary remains forecast just off the East Coast of the
CONUS and into the eastern Gulf of America serving as a focus for enhanced
precipitation. Uncertainty lies in how far inland the heaviest precipitation
extends, with the uncalibrated 0z ECENS and GEFS keeping the highest week-2
precipitation totals just offshore. The ECENS has trended drier compared to
yesterday across the Northeast due to surface high pressure depicted over the
region, with the corresponding PET indicating probabilities of 20 percent or
higher for 3-day precipitation totals exceeding the 85th climatological
percentile and 1-inch across the coastal Carolinas and Southeast. The GEFS
depicts the surface high over the Great Lakes resulting in elevated
probabilities extending further into the Mid-Atlantic and coastal New England
in the GEFS PET. Given the uncertainty to the north, the slight risk of heavy
precipitation is limited to the coastal Carolinas, Southeast, and the Florida
Peninsula, Sep 11-13.



Surface high pressure across the Northeast also favors enhanced easterly flow
along much of the Eastern Seaboard, with the ECENS PET depicting a 20 percent
chance of wind speeds exceeding the 85th climatological percentile and 25-mph.
This supports a slight risk of high winds for portions of this region, Sep
11-15. A moderate risk was considered across the coastal Carolinas and Georgia
early in week-2 where the ECENS PET indicates probabilities for wind speeds
exceeding the 85th climatological percentile greater than 40 percent. However,
the GEFS has a notably weaker signal, supporting only maintaining the slight
risk. It is not out of the question to have an area of surface low pressure
spin up along the frontal boundary off the East Coast during week-2, which
could exacerbate impacts along the coast. The National Hurricane Center
continues to monitor a tropical disturbance across the Atlantic Main
Development Region with high chances for tropical cyclone formation in the next
week. Most model guidance continues to depict a recurving track away from the
coast.



Mid-level troughing and associated surface low pressure across the Bering Sea
and western Alaska are forecast to bring periods of intermittent heavy
precipitation and high winds to south-central coastal Alaska during week-2. The
ECENS PET depicts at least a 20 percent chance of wind speeds exceeding the
85th climatological percentile and 40-mph across southern coastal Mainland
Alaska during the early and middle parts of the period. Therefore a slight risk
is highlighted for high winds across this area, Sep 11-15. An associated heavy
precipitation hazard is not issued at this time given the uncertainty of
whether totals would reach hazardous criteria over a widespread area.

FORECASTER: Thomas Collow

$$