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FXUS21 KWNC 131819
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 13 2026

SYNOPSIS: A cool air mass is forecast for portions of the Northeast at the
onset of week-2 bringing chances for first frosts and freezes to parts of the
region. A stalled frontal system over the Mid-Atlantic and Southeast could
serve to bring heavy precipitation to the area. Another round of enhanced
mid-level moisture is favored to overspread the western CONUS, potentially
bringing heavy precipitation and possible flooding over portions of the Four
Corners. In Alaska, a potent area of low pressure is forecast in the Gulf of
Alaska that may bring chances for heavy precipitation to portions of the
southeastern Mainland and Southeast Alaska.

HAZARDS

Slight risk of much below normal temperatures for parts of northern New
England, Mon, Sep 21.

Slight risk of heavy precipitation for portions of the Southeast and
Mid-Atlantic, Mon-Wed, Sep 21-23.

Slight risk of heavy precipitation for the Four Corners region, Mon-Wed, Sep
21-23.

Slight risk of heavy precipitation for parts of Southeast Alaska and
southeastern Mainland Alaska, Mon, Sep 21.

Flooding possible for portions of the Desert Southwest, Great Basin, and
Rockies.

DETAILED SUMMARY

FOR WEDNESDAY SEPTEMBER 16 - SUNDAY SEPTEMBER 20:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY SEPTEMBER 21 - SUNDAY SEPTEMBER 27: The GEFS, ECENS and CMCE remain
in good agreement in regards to the evolution of the 500-hPa pattern next week.
A mid-level ridge amplifies over central and eastern Canada during week-2
bringing positive height anomalies back to the central and eastern contiguous
U.S. (CONUS) with time. A longwave trough is forecast upstream over the Gulf of
Alaska and along the West Coast.



Tied to a transient trough progressing through the northeastern CONUS, a slight
risk of much below normal temperatures remains posted for northern New England
valid for Sep 21. Within the highlighted areas, there continues to be agreement
in uncalibrated temperature tools showing increased chances for temperatures
falling below 40 deg F, with the ECENS Probabilistic Extremes Tool (PET)
favoring 20-30% chances of minimum temperatures falling below the 15th
climatological percentile. While near freezing temperatures are not markedly
unusual for this time of year (climatological first freezes occur by late
September for the highlighted areas), any frost and/or freezes associated with
the favored cold air mass may be impactful to some vegetation.



Model guidance has come into better agreement today for an elevated chance of
heavy precipitation for parts of the Southeast and Mid-Atlantic. A lingering
frontal zone is forecast across the region and southerly return flow could
bring enhanced moisture into the region. The PETs from the GEFS and ECENS both
highlight increased chances for precipitation to exceed the 85th climatological
percentile and 1 inch in this region. Similarly, the uncalibrated guidance has
also seen an increase in signal strength over the past 24 hours. Therefore, a
slight risk of heavy precipitation is posted for Sep 21-23 for parts of the
southern Mid-Atlantic and Southeast.



Weak troughing and onshore flow favored near the West Coast along with the
potential for additional tropical moisture from the eastern Pacific, a slight
risk of heavy precipitation remains posted (Sep 21-23) over the Four Corners
where uncalibrated tools maintain elevated chances for 3-day precipitation
amounts exceeding a half an inch, and in some locations more than one inch. In
addition, given the continued indications of potentially heavy precipitation
during the next week or so, a possible flooding hazard remains posted for
portions of the Four Corners. This region is prone to flash flooding and
caution should be exercised near canyons and creek beds.



Multiple model ensembles depict surface and mid-level low pressure over the
Gulf of Alaska at the end of week-1 and into early week-2 resulting in enhanced
onshore flow and the potential for heavy precipitation along portions of the
southern and southeastern coast of Alaska. The model guidance indicates the
potential for 3-day precipitation totals to approach hazardous criteria with
widespread strong probabilities of 3 day precipitation amounts exceeding 2
inches and isolated areas of more than 3 inches throughout much of southeastern
Alaska. Therefore, a slight risk of heavy precipitation is posted from the
Kenai Peninsula through all of Southeast Alaska for Sep 21.



Across the central and eastern Pacific, the National Hurricane Center (NHC) is
currently monitoring TC Norbert, as well as a separate watch area located near
115W with a 90% chance of development during the next week. This developing
feature may be a factor in regards to the enhancing moisture advection into the
CONUS during week-2. A continued westward track from Norbert or its remnants
beyond the official forecast track from NHC, as well any other disturbances in
the proximity of Hawaii may pose an additional heavy precipitation threat to
the state during the next few weeks. Any additional precipitation may worsen
already saturated grounds across parts of Hawaii, following the impacts
associated with TCs Lowell, Moke, and Lala this season.

FORECASTER: Ryan Bolt

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