198
FXAK02 KWNH 150000
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
659 PM EST Thu Nov 14 2024

Valid 12Z Mon Nov 18 2024 - 12Z Fri Nov 22 2024

...Potential for strong winds and heavy snow over parts of
northwestern Mainland Alaska around the middle of next week...

...Overview...

Clear and cold conditions across much of mainland Alaska early
next week will give way to moderating temperatures and
increasingly stormy weather for western and northwestern Alaska
heading into midweek as an increasingly amplified pattern
develops.  The cold upper low lingering northeast of Alaska early
next week will give way to a strong ridge building into the
Aleutians/Bering Sea, followed by the arrival of an amplifying
trough from Siberia, which will work its way west against the
amplifying ridge.  The gradient between the strong ridge and the
digging trough from Siberia will bring a long fetch of moist
southerly flow across the Bering Sea, bringing the threat of high
winds and areas of heavy snow into the northwestern mainland
beginning Tuesday and through midweek.  Meanwhile, a low pressure
wave passing just south of the Aleutians around Sunday is forecast
to develop into a more expansive and robust cyclone as it dips
southeast and then tracks east along 50N latitude.  It appears
that the much of the impactful precipitation associated with this
system will pass just south of the Panhandle through midweek next
week.


...Guidance Evaluation/Preferences...

Model guidance especially the ensemble means today are showing
excellent agreement on increasingly amplified upper-level ridge to
propagate eastward across the Bering Sea early next week.
Meanwhile upstream from the ridge, guidance also shows an
upper-level trough located across eastern Siberia will begin to
dig east towards the amplifying ridge.  This is when the model
solutions begin to diverge.  The ECMWF and to some degree the
latest runs from the GFS show that the Siberia trough will be able
to erode the robust ridge downstream to allow a better chance for
a warm front and eventually a cyclone to push east into mainland
Alaska through midweek.  This would allow the high winds and areas
of heavy snow associated with the system to reach western and
northwestern Alaska earlier than previous forecasts.  This has
also opened up the possibility for these hazardous weather
conditions to penetrate further into the Mainland the subsequent
days.

The WPC forecast package was based on 40% from the 12Z ECMWF and
00Z EC mean, 40% from the 12Z GFS and GEFS, as well as 20% from
the 12Z CMC and CMC mean.  This blend yielded a solution with the
Siberian cyclone pushing farther east into western and
northwestern Alaska early to middle next week, but not as
aggressive as the latest 12Z run from the ECMWF.


...Weather/Hazards Highlights...

The southern coast and Panhandle may see some lingering mostly
light precipitation as low pressure persists over the Gulf of
Alaska into Monday.  A modest system brushing the Aleutians around
Sunday should bring a brief period of moderate totals there before
dropping southeastward into the east-central Pacific as it
develops into a larger scale low.  The low will likely remain far
enough south to keep most of the surrounding flow of moisture from
reaching much farther north than the southern Panhandle which may
see some moderate amounts.  Lighter/more scattered activity may
reach into the northern Panhandle/Southcentral coast.  Some
locations near the Alaska Peninsula may see brisk winds with gap
wind enhancements into Monday behind the Gulf low.  Winds may
strengthen along the southern coast/Panhandle early-mid week
within the tightening gradient between Mainland Alaska/western
Canada high pressure and the Pacific low.  By the middle of next
week, there appears to be an increasing threat for high winds
accompanied with terrain-enhanced heavy snow across northwestern
Alaska ahead of a cold front pushing across the Bering Sea, with
the possibility of earlier arrival of these threats, as well as
farther eastward penetration of these threat for subsequent days.

Meanwhile, much of mainland Alaska will begin with analogously
cold conditions Monday under clear skies.  The cold conditions
will persist into Wednesday morning over the eastern Interior.
Interior locations could reach at least as cold as 20-30F below
zero.  Temperatures should trend warmer Wednesday-Thursday as high
pressure moves east into Canada and a long fetch of moist and
milder southerly flow ahead of a front penetrates the western
mainland.

Kong/Rausch


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

$$