Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 021352
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
452 AM AKST Fri Dec 2 2016

.ANALYSIS AND UPPER LEVELS...
A deformation zone has formed in the Cook Inlet area caught
between a low in the Gulf and a trough slowly pushing through
southwest Alaska. The deformation zone is bringing snow to areas
around Cook Inlet. Along the north Gulf coast showers are moving
through the area from east to west due to the Gulf low. Out west,
north to northwest flow dominates bringing showers to much of the
Bering and Aleutians.

&&

.MODEL DISCUSSION...
The models are in good agreement with the main synoptic features
with only small differences with timing. However, these
differences should result in few, if any, impactful changes.

&&

.AVIATION...
PANC...Snow will taper off throughout the morning as the
deformation zone over the area continues to diminish. Then by
this evening outflow winds will increase out of the north bringing
gusts near 30 KT to the airport. There does remain some
uncertainty in the timing of the onset of the winds but there is
high confidence of stronger northerly winds overnight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Offshore west to northwesterly flow will build rapidly through
the day today as the surface low in the eastern Gulf of Alaska
tracks northwest and settles near Yakutat this evening. This flow
will also be aided as the cold upper trough and its associated
arctic air over western Alaska pushes east. Kodiak Island in
particular will see rather strong wind gusts, with gusts over 60
mph possible. Other land locations such as Whittier, Thompson
Pass, Valdez, and Seward will also see rather gusty conditions.
Storm force winds are expected over several of the marine zones.

Precipitation will taper off today over the Cook Inlet area as
the dynamics responsible for the recent snow dissipate. There
could be some lingering showers through late Friday night as cold
advection and west-northwest flow in the lower levels pushes the
remaining moisture up against the mountains.

As the colder air progresses into the area, wind chills could
become an issue Saturday night along the Alaska range in the
northern Susitna and Copper River basins.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Frigid temperatures will be the primary forecast concern across
the southwest mainland into the weekend beneath mostly clear skies
as an arctic air mass filters into the region in northerly flow in
the wake of the departing trough. Predominantly dry conditions
will prevail for the next several days as high pressure builds
overhead, although a few showers may persist along the western
slopes of the Alaska and Aleutian Ranges aided by orographic
enhancement. A disturbance tracking through the central Bering
may also bring a few snow showers to the Kuskokwim Delta coast
today, although the bulk of the active weather is expected to
remain offshore.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Strong cold air advection on the back side of the trough
departing into the Gulf of Alaska will continue to yield storm
force winds over the coastal waters west of Kodiak Island through
this afternoon, with a few hurricane force gusts possible through
channeled terrain along the coast. The cold northerly flow will
also help to generate convective snow showers along the Alaska
Peninsula as it passes over the still relatively warm waters of
the Bering. A compact polar low which has formed in the cold air
mass over the northwest Bering will then keep the active weather
going through tonight as it tracks quickly to the southeast
towards the Akpen. This feature will have the potential to produce
gusty winds and short lived, locally heavy snow as it moves over
the Pribilofs, bringing minor accumulations to the Pribilofs as
well as the Eastern Aleutians and Akpen. Attention then turns to
a storm force front entering the Western Aleutians tonight and
moving over the central part of the chain on Saturday.
Precipitation will quickly change over to rain or a rain/snow mix
as the front moves eastward accompanied by warm advection in deep
southerly flow. The eastward progress of the front will begin to
slow by Saturday as it encounters the building ridge over the
southwest mainland, keeping the most active weather over the
central and eastern Bering through the weekend.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The coldest weekend of the season is anticipated for this weekend
across much of mainland Alaska. High pressure will continue to
build in across mainland alaska, with low pressure remaining in
the Gulf of Alaska. This will help to support strong gusty
offshore flow across much of the Gulf of Alaska, with particularly
strong winds occurring across Kodiak Island, Shelikof Straight,
and the Barren Islands. By Saturday afternoon wind gusts will
continue to build through Thompson Pass and the Valdez area, as
pressure gradients increase, and very cold interior air builds.

By early next week, a pattern change will begin to bring slightly
warmer temperatures back to the Alaska mainland as a trough begins
to push across the southwest mainland. This will help to bring
more moderate temperatures to the region with widespread clouds
and southerly flow across the Southwest Mainland. It will also
help to dramatically decrease the pressure gradient between the
mainland and Gulf of Alaska and greatly diminish the offshore
flow and strong cold air advection.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Storm Warning 130 131 132 136 138 150 175 176 177 178.
Gale Warning 120 121 127 128 137 155 160 165 170 171 172 173 174
 185.
Heavy Frz Spray 130 138 140 160 180 181.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...MC



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