509
FXUS21 KWNC 301914
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 30 2025

SYNOPSIS: Dynamical models are in good agreement regarding anomalous mid-level
low pressure across the eastern contiguous U.S. (CONUS) at the outset of
week-2. Enhanced chances of heavy snow and below-normal temperatures are
favored to persist across parts of the Great Lakes and Northeast early in the
period. Mid-level low pressure forecast across the northeastern Pacific and
Alaska favors enhanced onshore flow across much of western North America
leading to elevated chances of heavy precipitation, high elevation heavy snow,
and high winds over parts of the northwestern CONUS into Southeast Alaska.
Diverging model solutions regarding the positioning of amplified mid-level
features across the CONUS reduces confidence toward the middle of the period.

HAZARDS

Slight risk of heavy snow across the Cascades, Mon-Wed, Dec 8-10.

Slight risk of heavy snow across the northern Rockies, Mon-Wed, Dec 8-10.

Slight risk of heavy snow across the Upper Peninsula of Michigan and western
portions of Lower Michigan, Mon-Tue, Dec 8-9.

Slight risk of heavy snow across portions of the interior Northeast and
Mid-Atlantic, and Central Appalachians, Mon-Tue, Dec 8-9.

Slight risk of much below normal temperatures across portions of the Upper
Mississippi Valley and western Great Lakes, Mon-Tue, Dec 8-9.

Slight risk of much below normal temperatures across portions of Upstate New
York and northern New England, Mon-Tue, Dec 8-9.

Slight risk of heavy precipitation across portions of the Pacific Northwest and
far northwestern California, Mon-Wed, Dec 8-10.

Slight risk of high winds across the northwestern CONUS into the northern and
central High Plains, Mon-Wed, Dec 8-10.

Slight risk of high winds across southeastern Alaska, Mon-Sun, Dec 8-14.

DETAILED SUMMARY

FOR WEDNESDAY DECEMBER 03 - SUNDAY DECEMBER 07:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY DECEMBER 08 - SUNDAY DECEMBER 14: The 0z ECWMF, GEFS, and Canadian
ensembles all depict anomalous 500-hPa troughing across the East during week-1
and into week-2. As a result, several shortwave impulses are forecast to
traverse the CONUS favoring an active weather pattern across the East. The
interaction between the southern and northern streams will ultimately determine
the placement of wintry weather, with the potential for a system moving through
every couple of days. This progression of shortwaves supports maintaining a
slight risk of heavy snow across portions of the Great Lakes, interior
Northeast, and extending along the Allegheny Front, Dec 8-9, with heavy snow
either directly from the individual systems or Lake Effect.



Along with the potential for snow, is the possibility of much below-normal
temperatures. The ECMWF Probabilistic Extremes Tool (PET) depicts parts of the
Upper Mississippi Valley, Great Lakes, and Northeast having at least a 60
percent chance minimum temperatures fall below the 10th climatological
percentile. This would correspond to elevated chances of subzero temperatures
over portions of the Upper Mississippi Valley and the interior Northeast, with
negative teens possible across northern Minnesota and North Dakota. Taking wind
chill into account, some of these areas may reach NWS Cold Advisory criteria
supporting a slight risk for much below normal temperatures, Dec 8-9. The GEFS
is less amplified with the initial troughing compared to the ECMWF and Canadian
ensembles and is also the quickest to flip to a more typical La Nina pattern
later in week-2, with ridging developing over the Southeast and more troughing
in the West. The GEFS scenario would result in a relatively more tranquil
pattern with warmer conditions returning to the East by mid-December. However,
the ECMWF and Canadian solutions would favor a persistence of the current
colder and stormy pattern. Given the uncertainty, no hazards are posted across
the East beyond day-9 (Dec 9).



Troughing over the northeastern Pacific and Alaska during week-2 favors
increased onshore flow and as a result, elevated precipitation chances across
portions of western North America. The uncalibrated ECMWF ensemble depicts
24-hour precipitation totals upwards of 1 to 1.5 inches across coastal areas of
Washington and northwestern Oregon on days 8 and 9 (Dec 8-9), with a
corresponding uptick in probabilities for Integrated Vapor Transport (IVT)
values to exceed 250 kg/m/s compared to yesterday. While the GEFS precipitation
values are lower compared to the ECMWF ensemble, enhanced precipitation extends
farther south into California given the transition to more troughing in the
West by the middle of the period. However, further complicating the forecast,
the ECMWF and Canadian ensembles depict a more amplified ridge across the West
Coast of the CONUS which would favor less precipitation over the Southwest. A
slight risk of heavy precipitation is posted across the Pacific Northwest into
far northwestern California, Dec 8-10. Accompanying slight risks of heavy snow
are posted across the Cascades and northern Rockies for the same time frame.
The GEFS would support an extension of the heavy precipitation and snow risks
further south into California and the Sierra Nevadas respectively, but holding
off due to the aforementioned model discrepancies. A broad slight risk for high
winds is also highlighted from the northwestern CONUS into the northern and
central High Plains tied to the increased pressure gradient and supported by
the ECMWF and GEFS PETs.



Below-normal temperatures are likely across Alaska associated with troughing
over the state, although NWS Cold Advisory criteria is unlikely to be reached.
Periods of heavy precipitation and high winds are likely across Southeast
Alaska due to enhanced onshore flow. While precipitation totals in the PETs and
uncalibrated guidance do not reach hazards thresholds, the ECMWF PET depicts
parts of the region having at least a 20 percent chance wind speeds exceed
40-mph associated with mean surface low pressure over the Gulf of Alaska.
Therefore, a slight risk for high winds is posted across southeastern Alaska
for all of week-2.

FORECASTER: Thomas Collow

$$