161
FXAK02 KWNH 242340
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
635 PM EST Sun Nov 24 2024

Valid 12Z Thu Nov 28 2024 - 12Z Mon Dec 02 2024

...Wet/Snowy pattern setting up for the Southeast/Panhandle by the
Thanksgiving weekend as cold air prevails across the Interior...


...Guidance Evaluation/Preferences...

Model guidance continues to agree that a blocking omega
upper-level pattern across the Alaskan domain will become more
amplified with time as we head into the Thanksgiving weekend with
a closed-off anticyclone forming over northeastern Siberia while a
general storm track passes south of the Aleutians and heads toward
the Southeast/Panhandle by the weekend.  More specifically,
today`s deterministic guidance has trended toward a stronger ridge
axis across the Bering Sea through the Alaska Peninsula as the
medium-range forecast period begins midweek.  The ridge axis then
amplifies into an omega block pattern which subsequently evolves
into a detached upper high and meanders over northeastern Siberia
late this week.

Meanwhile, guidance today shows reasonably good agreement on the
depiction of a main storm track south of the Aleutians.  The
ensemble means depict that a large but weakening cyclone well
south of the Aleutians will track toward Alaska
Panhandle/Southeast late this week but with a slower forward
motion.  The fast model solutions yesterday have backed off
regarding this system.

Today`s WPC forecast package for Alaska was based on a consensus
blend of about 40% from the 12Z ECMWF and the 00Z/12Z EC mean, 40%
from the 12Z GFS/GEFS, and 20% from the 12Z CMC/CMC mean,
transitioning to mostly a blend of the ensemble means for Days 7 &
8.  This blend yielded a solution compatible with yesterday`s
forecast package, with lesser amounts and later arrival of QPF for
the Panhandle during the Thanksgiving weekend.


...Weather/Hazards Highlights...

Persistent northwesterly flow in the upper levels down the right
branch of an omega blocking pattern will maintain mostly clear and
cold conditions for interior Alaska with a cold high pressure
system at the surface.  Passing shortwave energy could develop a
front and bring some snow showers for the North Slope late this
week.  Much of the interior sections will be colder than normal,
with low temperatures possibly dipping to near -40 degrees at the
coldest spots in the eastern interior.  Milder than normal
temperatures are forecast for the North Slope as a more
southwesterly flow develops at the surface.

Modest amounts of precipitation associated with a weakening old
cyclone remain across the Panhandle as the medium-range period
begins midweek.  Meanwhile, the distance from the main cyclone
moving across the North Pacific will likely keep the heavy
precipitation from reaching the Aleutians, although a couple of
days of light to moderate rain under gale force east to
northeasterly winds can be expected across the southern Peninsula
to the eastern Aleutians by around Thanksgiving.  An increasing
chance of mountain snow and low-elevation rain can be expected to
overspread the Panhandle through the Thanksgiving weekend.
Precipitation could become heavy by next Monday as the offshore
cyclone edges closer toward the Panhandle and the southern
coastline.

Kong


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

$$