498
FXUS21 KWNC 271846
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 27 2025

SYNOPSIS: A broad area of mid-level low pressure over the higher latitudes of
eastern North America favors below-normal temperatures across the Midwest and
Northeast during early December. Additional heavy, lake-effect snow could
accompany any outbreaks of anomalous cold. The wet fall pattern for southern
California may continue into early December. A rapid transition from above to
below-normal temperatures remains likely for Alaska by December 5 or 6.

HAZARDS

Slight risk of much below normal temperatures for parts of the Upper
Mississippi Valley, Great Lakes, and Northeast, Fri-Sat, Dec 5-6.

Slight risk of heavy snow for parts of the eastern Great Lakes and Central
Appalachians, Fri-Sat, Dec 5-6.

Slight risk of heavy precipitation for portions of the Southeast, Fri-Sat, Dec
5-6.

Slight risk of heavy snow across the Northern to Central Rockies, Fri-Sun, Dec
5-7.

Slight risk of heavy precipitation for southern California and the Desert
Southwest, Fri-Sat, Dec 5-6.

DETAILED SUMMARY

FOR SUNDAY NOVEMBER 30 - THURSDAY DECEMBER 04:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY DECEMBER 05 - THURSDAY DECEMBER 11: The GEFS, ECENS, and GEFS are in
good agreement and remain consistent that a deep, closed 500-hPa low develops
over Hudson Bay at the beginning of December and then persists through the
early part of the month. This deep mid-level trough and cross-polar flow are
likely to result in below normal-temperatures across the Midwest and Northeast
from December 5-11. A slight risk of much below-normal temperatures (valid
December 5 and 6) is posted for parts of the Great Lakes, northern New York,
and New England where the GEFS and ECENS Probabilistic Extremes Tools (PETs)
have more than a 20 percent chance that minimum temperatures fall below the
10th percentile and 0 degrees F. Gusty winds, associated with the predicted
cold air advection, elevate the chance that the NWS Cold Advisory criteria may
be reached for those designated areas. Strong cold air advection is expected to
promote lake-effect snow later next week with a slight risk of heavy snow
posted for areas downwind of Lakes Erie and Ontario along with parts of the
Central Appalachians on December 5 and 6. The latest model guidance is
beginning to show a faster end to the lake-effect snow so this hazard may be
discontinued on Friday.



A wave of low pressure is expected to track along a stationary front across the
Southeast early in week-2. The timing of the heaviest precipitation is somewhat
uncertain with the GEFS one day slower than the ECENS, but both ensemble means
are in good agreement with more than a 20 percent chance of one inch of
precipitation from Louisiana northeast to the Southern Appalachians. This model
output supports a slight risk of heavy precipitation, valid for December 6 and
7. However, flooding concerns are low since this region has been
drier-than-normal during the past 30 to 60 days. If this wave of low pressure
can gain latitude and remain intact, then accumulating snow could occur across
the Central Appalachians and Mid-Atlantic around December 6. However, chances
for heavy snow are less than 20 percent at this time.



As is typical with shortwave troughs forecast to separate from the mid-latitude
westerlies and dig into the Southwest or offshore of southern California, the
precipitation outlook is uncertain for those areas late next week. However, the
ECENS and GEFS depict a 500-hPa trough or even cut-off low near southern
California which increases the chance of heavy precipitation for this area and
inland across the Desert Southwest. Based on the ECENS and GEFS PETs and their
uncalibrated model output, a slight risk of heavy precipitation is posted from
southern California east into Arizona through December 7. A longwave 500-hPa
trough along with support from the GEFS SWE PET and uncalibrated ECENS results
in a slight risk of heavy snow for parts of the Northern to Central Rockies
from December 5 to 7. For the Pacific Northwest and northern California,
forecast confidence continues to be too low to designate any hazardous
precipitation risks. With the northeastern Pacific ridge forecast to retrograde
west to the Aleutians, there could be an increasing chance of heavy
precipitation and snow for the northern half of the West Coast during the
second week of December. This will be closely monitored in subsequent week-2
hazards outlooks.



Following a retrogression of a mid-level ridge from the northeastern Pacific to
the Aleutians later next week, a quick transition from above to below-normal
temperatures remains likely for Mainland Alaska. Despite this major pattern
change, temperatures are not expected to reach NWS cold advisory criteria at
this time.

FORECASTER: Brad Pugh

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