Gale Warning 850, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
446 PM AKST Wed Dec 27 2023

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

Patchy fog has returned to portions of the Copper River Basin and
western Kenai Peninsula today. It will remain through tomorrow
morning. Elsewhere, a clear sky is expected to allow for low
temperatures to drop into the teens below zero across Southcentral
Alaska; lower in the typical colder spots. A ridge of high
pressure will remain in place tomorrow for most locations
resulting in dry conditions. However, northerly winds will stay
strong through the gaps in Whittier, eastern Kenai Peninsula and
Prince William Sound with gusts ranging from 30 to 40 mph through
Friday morning. Blowing snow could occur in these areas.

A low pressure system is working its way north and west into the
northern Gulf of Alaska as a front also moves across Kodiak Island
Friday. The front is trending to slow its speed and also turn
more negatively tilted. With a negatively tilted front, cold air
in place over the Copper River Basin and warm and southeasterly
air approaching from the storm, models have begun to depict a more
northwesterly track to the storm which could result in
precipitation in Prince William Sound, Anchorage area and Eastern
Kenai Peninsula this weekend. However, confidence on the exact
timing, type and location of precipitation remains low at this
time.

CQ/DJ

&&

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

Southwest Alaska is forecast to dry out as remaining shortwaves
weaken. After patchy overnight fog, conditions progress from
partly sunny on Thursday, to sunny on Friday as shortwave ridging
and offshore flow will lead to a return of clearer skis and cold
temperatures.

ER

&&

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

A complex pattern is evolving over the Bering as a strong front
moves over the Chain tonight. With an ample cold air pool,
precipitation along the front is expected to fall as snow,
transitioning to a rain/snow mix after frontal passage.

South to southeast winds will gust to around 60 mph. Temperatures
at 850 mb are -8C, increasing to -4C behind the front. While cold
enough for snow development, these strong southerly winds will
increase surface temperatures. This is expected to begin Wednesday
night for Adak, during the day on Thursday for Unalaska, and
Thursday night for the Alaska Peninsula. During this period it
will be possible for snow to reduce visibility down to one half
mile or less. Snow levels are forecast to be around 100 to 200 ft.

Throughout the day on Thursday multiple lows are expected to
develop along the front, leading to areas of gales to storm force
winds. As the system spreads out and becomes a complex low,
temperatures will continue to warm into the mid to upper 30s.

ER

&&

.LONG TERM FORECAST (Days 4 through 7: Saturday through Wednesday)...

The longwave trough extends from the Russian Far East across the
Bering and Southwest Alaska into the Gulf of Alaska through the
forecast period. This provides the track for several low centers
to move along a well developed front across the Aleutians and
Alaska Peninsula Monday through Wednesday. Forecast model
confidence is low due to differences in forecast strengths and
tracks. Widespread gale force winds with areas of storm force
gusts are forecast to move from the North Pacific into the Bering
by the end of the period. Precipitation starts as snow in the
colder air, but changes over to rain and snow mixed across the
region through mid-forecast period, and rain by the end. Periods
of locally heavy precipitation are expected across the AKPEN into
Southwest Alaska through Wednesday.

Weather over the Gulf of Alaska will be driven by low centers
that moves along the Southeast Panhandle into the Northern Gulf
through Wednesday. Gusty winds spread along the Alaska Peninsula
over Kodiak Island and along the North Gulf Coast. Northerly gale
force gap winds form through Cook Inlet, Barren Islands, Kamishak
Bay and Shelikof Strait Monday, and around Sitkinak for Tuesday. A
near gale force barrier jet forms along the North Gulf Coast by
Tuesday and Wednesday. Widespread precipitation extends from
Kamishak Bay along the Eastern Kenai Peninsula to the Canadian
Border through Wednesday.

Kutz

&&

.AVIATION...

PANC...The forecast challenge through the TAF period will be stratus
and fog. The environment is favorable for fog to form, with a steep
low level inversion and dry air aloft. The challenge is figuring
out timing of formation, whether it will move directly over the
terminal, and how long it will last. For now, have largely gone
with climatology, which favors fog forming after sunset and
expanding during the overnight hours. In addition, have strongly
hinted at fog without going all the way down to 1/2 mile
visibility in the TAF. Will wait until fog actually forms to add
more detail and lower conditions (if necessary). Bottom line,
updates will be made to the forecast based on trends in the
Anchorage area.

&&