897
FXUS21 KWNC 101958
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST December 10 2025

SYNOPSIS: Mid-level low pressure over Southeast Alaska downstream from a strong
mid-level high pressure ridge centered over the Bering Sea are forecast to
bring very cold air and dangerous wind chills across central and southern
Alaska, along with episodes of high winds across southern Alaska from the
Aleutians into Southeast Alaska. Enhanced onshore flow into the northern and
central West Coast of the contiguous U.S. (CONUS) is forecast to persist from
week-1 well into week-2 with mid-level low and high pressure to the north and
south of the region, respectively. An Arctic air mass is forecast to move south
of the Canadian border into the north-central CONUS, before progressing rapidly
eastward across the Great Lakes and Northeast. For much of the East however,
increased return flow from the Gulf is expected to moderate temperatures.

HAZARDS

Slight risk of high winds for southern Alaska from the central Aleutians
through Southeast Alaska, Thu-Wed, Dec 18-24.

Moderate risk of much below normal temperatures for Southeast Alaska, Thu-Sun,
Dec 18-21.

Slight risk of much below normal temperatures for much of central, eastern, and
southern Alaska, Thu-Tue, Dec 18-23.

High risk of heavy precipitation for southwestern Oregon and northwestern
California, Thu-Sun, Dec 18-21.

Moderate risk of heavy precipitation for the Pacific Northwest, Northern and
portions of Central California, Thu-Sun, Dec 18-21.

Slight risk of heavy precipitation for the Pacific Northwest and much of
California, Thu-Wed, Dec 18-24.

Moderate risk of heavy snow across the Cascades, Klamath, and Northern and
Central Sierras, Thu-Sun, Dec 18-21.

Moderate risk of heavy snow across the Northern Rockies, Thu-Sun, Dec 18-21.

Slight risk of heavy snow across the Cascades, Klamath, and the Sierras,
Thu-Wed, Dec 18-24.

Slight risk of heavy snow from the Northern Rockies southward into the Wasatch
Range in northern Utah, Thu-Wed, Dec 18-24.

Slight risk of heavy snow for much of the Colorado Rockies, Thu-Wed, Dec 18-24.

Moderate risk of high winds from the Pacific Northwest and Northern California
eastward to the Northern Rockies and eastern Intermountain Region, Thu-Mon, Dec
18-22.

Slight risk of high winds for most of the Western CONUS, Thu-Wed, Dec 18-24.

Slight risk of much below normal temperatures for the general vicinity of the
Upper Mississippi Valley, Fri-Mon, Dec 19-22.

Slight risk of high winds from the Great Lakes region to the Atlantic coast
from Maine southward to the Delmarva Peninsula, Thu-Mon, Dec 18-22.

Flooding possible across parts of the Pacific Northwest.

DETAILED SUMMARY

FOR SATURDAY DECEMBER 13 - WEDNESDAY DECEMBER 17:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY DECEMBER 18 - WEDNESDAY DECEMBER 24: The 0z ECWMF, GEFS, and
Canadian ensembles depict an amplified mid-level ridge centered over the Bering
Sea, with an amplified downstream mid-level trough established over Southeast
Alaska. At the surface, this set-up favors persistent high pressure across much
of Alaska and the Yukon throughout week-2. Conversely, mean low pressure is
favored in the Gulf of Alaska. The pressure gradient between these features
brings increased chances for episodes of high winds across much of southern
Alaska from the central Aleutian Islands through Southeast Alaska. High winds
would be particularly favored in gaps and inlets. Probabilistic Extremes Tools
(PETs) show enhanced chances of wind speeds exceeding the 85th climatological
percentile. Therefore, a slight risk of high winds (for all of week-2) is
posted for most of southern Alaska.



PETs continue to highlight enhanced chances for temperatures to fall to near
hazardous thresholds across portions of south-central, Interior, and Southeast
Alaska. As the Bering Sea ridge slowly weakens, the anomalous cold (and
associated northerly flow) will gradually expand westward across the state. A
moderate risk is posted for Southeast Alaska for Dec 18-21, while a broader
slight risk is maintained for much of the Interior, south-central, and
Southeast Alaska for most of week-2. Temperatures between -20 deg F and -35 deg
F are predicted to be widespread across much of inland Alaska, with -40 deg F
temperatures indicated by the PETs over the eastern Interior to the north of
Fairbanks. Closer to the coast, temperatures are expected to range between 0
and -15 deg F (Anchorage near -10 deg F), while the southern half of Southeast
Alaska is predicted to be somewhat milder, with high temperatures about +10 deg
F. The combination of very cold weather and high winds along the southern tier
of the state increases the threat for heavy freezing spray at times near larger
bodies of water.



The 0z ECENS, 0z GEFS, and 0z CMCE model solutions predict a fairly flat
mid-level flow pattern over most of the CONUS during the early and middle
portions of week-2. Thereafter, mid-level troughing over Southeast Alaska and
the Gulf of Alaska is forecast to dig southward off the West Coast, with the
most amplified solutions favored by the ECENS and CMCE solutions. Today`s ECENS
and CMCE solutions favor a storm track even farther south along the West Coast
than they did yesterday. The GEFS, which seemed too far north with the Pacific
jet and mean storm track yesterday, also shifts the storm track south today,
though not as far south or as amplified as the enhanced onshore flow in the
other two ensemble means. The PETs and uncalibrated precipitation guidance
supports a slight risk of heavy precipitation along nearly all of the West
Coast for Dec 18-24. A moderate risk for heavy precipitation is indicated for
the Pacific Northwest, Northern and portions of Central California from Dec
18-21. Additionally, a high risk of heavy precipitation is posted for
southwestern Oregon and northwestern California, also valid from Dec 18-21.
Precipitation amounts of 2 inches are predicted by PET guidance within this
broad region of elevated onshore flow from Washington state southward to
Central California. Near an inch of precipitation is indicated as far south as
the Los Angeles area. This forecasted heavy precipitation, in addition to the
antecedent week-1 precipitation is likely to aggravate flooding issues for the
Pacific Northwest, with a flooding possible hazard still posted. Depending on
what tomorrow`s model guidance shows, this flood hazard may need to be extended
farther south into Northern California. In areas of steep terrain or burn
scars, there is also the possibility of landslides.



As the incoming moisture (associated with an expected atmospheric river)
streams farther inland, periods of heavy mountain snow are predicted across the
Cascades, Klamath, Siskiyou, and Sierra Nevada Ranges, where a slight risk of
heavy snow is posted for the duration of week-2. A moderate risk of heavy snow
is posted for Dec 18-21 based on the uncalibrated ECENS snow tool indicating
elevated chances for snowfall exceeding a foot from the Cascades to the Central
Sierras. A slight risk for heavy snow is also posted farther inland from the
Northern Rockies southward into the Wasatch Range of Northern Utah, Dec 18-24.
Encompassing much of this area is a moderate risk of heavy snow for the
Northern Rockies, Dec 18-21. Finally, a slight risk of heavy snow is indicated
for much of the Colorado Rockies, with periods of heavy snow possible
throughout week-2.



An increased pressure gradient across much of the western CONUS, supported by
the PET wind tool warrants a slight risk of high winds over this widespread
region from Dec 18-24. Embedded within this area, a moderate risk of high winds
is posted from the Pacific Northwest and Northern California eastward to the
Northern Rockies and eastern Intermountain Region, Dec 18-22. PETs indicate
wind speeds in excess of the 85th climatological percentile and at least 20-25
mph. These wind speeds will be reassessed tomorrow, along with the increasing
potential for a significant atmospheric river over the West during week-2.



Temperatures across the East are expected to moderate as the week-2 period
progresses, coincident with a predicted rapid flattening of the 500-hPa flow
pattern and the migration of surface high pressure off the Southeast coast.
This favors increasing return flow from the Gulf of America, with non-hazardous
precipitation overspreading much of the Lower Mississippi and Tennessee Valleys
early in the period. In early week-2, a shallow undercutting Arctic air mass is
depicted by the models to rapidly progress south of the Canadian border into
the Dakotas, Upper Mississippi Valley, and western Great Lakes region.
Thereafter, this air mass is predicted to be escorted rapidly eastward across
the remainder of the Great Lakes and the Northeast by fast westerlies, with
little additional southward penetration. Accordingly, a slight risk of much
below-normal temperatures is indicated over the vicinity of the Upper
Mississippi Valley, Dec 18-22.  The uncalibrated GEFS and ECENS tools briefly
support wind chill values near -20 deg F in this area, and actual air
temperatures in the single digits above zero. Finally, enhanced wind speeds are
favored from the Lakes region eastward to the Atlantic coast from Maine
southward to the Delmarva Peninsula, with PETs predicting speeds exceeding the
85th climatological percentile and 20-25 mph. This is related to low pressure
passing north of the Great Lakes during the first and middle portions of the
forecast period, and surface high pressure centered over/near the Tennessee
Valley.

FORECASTER: Anthony Artusa

$$