Gale Warning 738, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
1035 AM AKST Wed Dec 18 2019

.ANALYSIS AND UPPER LEVELS...

A large area of low pressure continues to encompass the entirety
of the Gulf of Alaska. The actual low center is well defined on
satellite and continues to slowly move east to southeast across
the southern gulf. It is currently located about 500 miles south
of Kodiak Island. The latest front it has spun north to the Gulf
Coast remains nearly stationary and is decaying in place, with
just some showery precipitation. As with the previous front a few
days ago, it is unable to push inland, though some upper level
cloud cover has made it over the Chugach. One interesting feature
is a compact low that has spun up along this front and is moving
westward along the coast.

Also of note, colder air has begun to move into southern Alaska
from the Interior. It is most noticeable in the Bering, with
northerly flow distinctly pushing cloud cover south. There are
even cirrus banner clouds on satellite emanating from volcanic
peaks in the Aleutians...evidence of this strong flow. Cold air is
also noticeable in the Copper River Basin, where temperatures are
already below zero.

&&

.MODEL DISCUSSION...

Models are still on their run of good agreement and pegging the
forecast. This uncommon occurrence of sustained model consistency
makes for little change in the forecast from yesterday and a high
confidence level. Later in the week, models do differ a touch on
placement of the surface low in the gulf as it tracks east, but
differences are not enough to affect the forecast.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

After a number of days of very little change in the pattern over
Southcentral, we will start to head into a pattern change. The
seemingly perpetual front along the North Gulf coast is still
there today. A tightly packed closed low has developed along it
near Middleton Island early this morning. This low will continue
westward and should dissipate by the afternoon, however there will
be Gale force winds around it with the potential for a few higher
gusts toward storm force this morning. These higher winds likely
will only be in a small region close to the low.

By Thursday, there should be higher pressure and colder air moving
into Southcentral from the northwest and gusty northerly winds
developing around Prince William Sound, which will spread over the
eastern Kenai Peninsula as well by Thursday night. This will usher
in the pattern change to a colder and drier airmass for the
remainder of the week across all of Southcentral.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Friday)...

Cold and dry weather will continue to be the theme of the forecast
through Friday. High pressure over interior Alaska coupled with
a Gulf low will keep northerly winds ongoing through Friday. This
will allow increasingly cold air to move into Southwest Alaska.
Highs today in the single digits across the Kuskokwim Valley and
Delta will drop below zero Thursday. Meanwhile lows tonight and
Thursday night will fall to the 10 below to 20 below range. North
to northeasterly winds will persist through Thursday, particularly
over Bristol Bay east of Dillingham, and through Bethel and along
the Kuskokwim River. Wind chills in the 20 below to 35 below range
are expected across much of Southwest Alaska both tonight and
Thursday night. Those sensitive to those very chilly temperatures
should take the proper precautions to avoid prolonged exposure to
the cold.

On Friday, a quickly weakening front will move into the Kuskokwim
Delta during the day. A quick 1 to 3 inches of snow will be
possible, with the highest amounts along the coast. It will
dissipate as it tries to cross the Kuskokwim Mountains Friday
night. Associated cloud cover will be a brief reprieve from the
most brutal cold, as temperatures rise above zero for most of the
Kuskokwim Delta and Bristol Bay on Friday. However, sub-zero
temperatures will persist over the Lower Kuskokwim Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Friday)...

While northerly winds help produce rain and snow showers over
much of the eastern Bering, a gale force front will be moving into
the western Bering later today. The front will slowly cross the
Bering through Friday weakening as it goes. It will dissipate as
it moves into Southwest Alaska. Behind the front, high pressure
builds into the central Aleutians, turning the flow westerly over
most of the Bering. A reinforcing shot of cold air will also
follow behind the front. Snow showers will therefore also be
common in the post-frontal air mass.

&&

.MARINE (Days 3 through 5)...

Reasonable confidence in model guidance has colder air and
outflow patterns setting up along the northwest Gulf Coast
adjacent to Kodiak Island Saturday into Sunday, then diminishing.
Small craft winds with isolated gales are likely in the vicinity
of the Barren Islands. Model solutions are coming to greater
agreement on a North Pacific low tracking along the Aleutians with
storms and gales Saturday through Monday. This will kick off an
active period along the Aleutian Chain. Another low is expected to
come behind the previous low on Monday evening. Model solutions
for its strength are somewhat vague at this moment.

&&

.LONG TERM FORECAST (Days 3 through 7)...

Guidance indicates a quiet weather pattern kicking off the period
for the end of the week on mainland Alaska with an arctic trough
spilling cold air across most of southern Alaska, thus more winter
like temperatures and potential for snow. The Aleutian Chain will
see a series of lows track across them Saturday through
Wednesday. Guidance suggests right now a strong likelihood for
these systems to remain offshore and track along the coast of
Southcentral Alaska. Models generally agree on a pattern change
that has precipitation chances picking up for Bristol Bay and the
AKPEN on Sunday afternoon, then spreading across Coastal
Southcentral Alaska through Tuesday. Reinforcements to
precipitation are expected on Wednesday as well, as another system
arrives. There is moderate confidence that some snow will fall
due to cold air in place across Southern Alaska.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES: 120 131 172 176-178 411
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BJB
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
MARINE/LONG TERM...LTB