Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
621 PM EST Thu Dec 02 2021
Valid 12Z Mon Dec 06 2021 - 12Z Fri Dec 10 2021
...Heavy snow and high wind threat from western to southern Alaska
into early next week...
...Overview and Guidance Evaluation/Preferences...
The Alaskan weather pattern will become increasingly active
through this weekend and into early next week as amplified upper
troughing brings a deep cyclone and reinforcing energies across
the Bering Sea to western Alaska. The system should weaken as it
tracks through the Mainland though additional triple point
development along the Gulf Coast should send a cold front towards
the Panhandle region mid week. Meanwhile, an additional upper
trough energies tracking towards the Bering Sea and Aleutians by
later next week may support another deep low pressure system into
the region, albeit with more uncertainty.
Guidance shows relatively good agreement through Day 4/5
(Monday/Tuesday) and a composite of the well clustered 12 UTC
GFS/ECMWF/Canadian seems to offer a reasonable solution with above
normal detail and predictability. Forecast spread and uncertainty
increases quickly days 6-8 (Wed-next Friday), especially
surrounding the next main low towards the Aleutians and Bering
Sea. The GFS/CMC and ensemble means still support lifting the low
to the Bering Sea, while the ECMWF tracks the low along/south of
the Aleutians.
Given trends and uncertainty, the WPC forecast progs used a blend
of the reasonably compatible GEFS/ECMWF ensemble means. This
approach maintains good continuity with yesterday's WPC forecasts
as well.
...Weather/Hazard Highlights...
The Bering Sea cyclone will usher in a much more active weather
pattern across Alaska consisting of windy and snow conditions.
Much of western Alaska will experience snow into Monday, with the
greatest threat across parts of the Seward Peninsula and
southwestern Alaska. Current guidance suggests some locations
could see upwards of a foot of snow, along with a period of gusty
winds as the low moves inland on Monday. Increasingly wet weather
will also move into parts of the Southern Coast and southeast
Alaska Monday into Tuesday again with a threat for locally heavy
snows, especially across the favorable terrain. The cold front
propagating through the Gulf should bring increased rain chances
to the Panhandle mid week next week with rain again threatening
the Aleutians as well with the next low pressure system into the
region.
After a period of much below normal temperatures, conditions
should finally begin to moderate from west to east by the start of
the extended period on Sunday as the Bering Sea low brings milder
air in from the south. By next Monday, much of interior and
northern Alaska should see temperatures near or above normal, with
the greatest anomalies likely across parts of western Alaska and
the North Slope region before some potential for western Alaskan
cooling later next week.
Schichtel
Hazards:- Heavy precipitation across portions of mainland Alaska,
Mon, Dec 6.
- Heavy snow across portions of mainland Alaska, Sun, Dec 5.
- High winds across portions of mainland Alaska, Sun-Mon, Dec
5-Dec 6.
- Much below normal temperatures across portions of mainland
Alaska, Tue-Thu, Dec 7-Dec 9.
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html