Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
658 PM EST Tue Nov 26 2024

Valid 12Z Sat Nov 30 2024 - 12Z Wed Dec 4 2024

...General Overview...

A rather blocky upper level flow pattern is expected to be in
place across the Alaska domain for the weekend after Thanksgiving,
with a cut-off upper high over eastern Siberia.  A well defined
upper low pinches off from the broader trough axis situated over
northwestern Canada, and then slowly retrogrades southwestward
towards the southern Bering around the upper high by Monday.  This
upper low will likely spur surface cyclogenesis over the Gulf
region by the middle of next week.  Before that, a separate low
pressure system over the Gulf this weekend is likely to bring
enhanced onshore flow and rounds of heavy rainfall for the
southeast Panhandle region, and a +PNA pattern is expected to be
in place across western Canada with an upper ridge axis in place
across British Columbia.

...Guidance Evaluation/Preferences...

The 12Z model guidance suite features reasonably good synoptic
scale agreement across the Alaska domain on Saturday, with good
overall clustering with the upper low crossing southwest across
Alaska through the weekend.  There has been a slight northwestward
trend in the guidance with this low compared to the 00Z guidance. 
The models are also in good agreement with the upper high situated
across the western Bering and far eastern Siberia.  However, the
region with the greatest model differences is across the Gulf
region and the timing of multiple shortwave impulses that will
affect the southeast portion of the state.  Overall, the CMC and
to a lesser degree the UKMET showed the greatest amount of
deviation from the ensemble means and the operational GFS/ECMWF
across that area, although they are more in line with the model
consensus elsewhere. Model differences become more widespread and
significant going into next Wednesday, and thus the ensemble means
accounted for a majority of the model blend by that time.

...Weather/Hazards Highlights...

Periods of moderate to heavy rain are expected to make weather
headlines across the southeast Panhandle for the first few days of
December as a potential atmospheric river event sets up and brings
several inches of rainfall across the windward terrain. This may
lead to enhanced run-off and rises on area rivers.  Elsewhere
across the state, the majority of the mainland should remain dry,
except for a few snow showers at times across the Alaska Range and
points south.  Windy conditions are likely for the Alaska
Peninsula and the eastern Aleutians on Saturday with a strong
pressure gradient in place.  Frigid temperatures are expected for
much of the Interior and the Brooks Range, with overnight lows
dropping into the -20s and even -30s in the normally colder valley
locations, and highs only recovering to the -0s and -10s for the
upcoming weekend.  The good news is a moderating trend is likely
to commence going into early next week as the upper ridge axis
from western Canada tries to build in, and more of a maritime
influence develops across southern Alaska.

Hamrick

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