Gale Warning 61, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
454 PM AKST Mon Jan 10 2022

.ANALYSIS AND UPPER LEVELS...

An elongated upper-level low is currently situated over the
central Aleutians. This feature is supporting a surface low south
of Nikolski that is continuing to move northwest toward Atka.
Rain is being reported for locations just east of this low, as a
southerly flow is advecting warmer air from the North Pacific. The
warm front from this feature extends to the northwest as well,
clearly visible on visible satellite as a boundary between
stratiform clouds over the central Bering and open-cell cumulus
clouds, a sign of colder air, moving south across the western
Bering and Aleutians. As of this afternoon, it is 43F in Dutch
Harbor and raining and 28F in Shemya and snowing.

Farther east, another surface low has moved northwest across the
Barren Islands and is now weakening as it runs into the Alaska
Range. Its associated front extends along the Southcentral coast
with rain continuing to fall along the immediate coast and snow
away from the coast as well as sheltered locations such as Valdez
and higher elevations. A strong, southeasterly cross-barrier flow
has kept much of the precipitation away from locations in the lee
of the mountains, where only occasional flurries have reported for
Anchorage.

With the front yet to push inland, northerly gap winds continue
from Thompson Pass to the Copper River Delta. Elsewhere, north to
northeasterly winds persist from Kenai and Anchorage north across
the Mat-Su Valleys. However, the intensity of these winds is
beginning to wane.

&&

.MODEL DISCUSSION...

Models continue to have decent agreement with the larger upper-
level and surface features through midweek. The main issue,
remains the slight discrepancies with respect to the progression
of various upper-level shortwaves embedded in the overall
southerly synoptic flow. The most recent 12z runs have come into
better agreement with a wave lifting north across Southcentral
Tuesday morning. This agreement has brought higher confidence to
the potential for light snow from Kenai north to Talkeetna and
across the Copper River Basin for Tuesday morning. However, a
subsequent wave lifting north for late Wednesday has yet to be
fully resolved, especially in the 18z runs. Thus, forecast
confidence, especially for another round of light snow over the
aforementioned areas, is below average by midweek.

&&

.AVIATION...

PANC...Northerly wind gusts will abate this afternoon, with winds
becoming lighter by evening. VFR ceilings will persist through
the day, with occasional flurries possible around the terminal.
Ceilings and visibility are both expected to drop to MVFR or IFR
by early Tuesday morning as light snow develops across the
Anchorage Bowl.

&&

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

Two weakening surface lows, one near the Barren Islands and a
second south of Middleton Island will both move inland tomorrow
morning. This will spread precipitation into the Cook Inlet region
and Susitna Valley while also maintaining the onshore flow
necessary for sustained precipitation over coastal areas of the
Gulf. Prince William Sound and eastern Turnagain Arm will likely
remain rain or a rain/snow mix through early tomorrow afternoon
at sea level, with Cordova and Seward keeping warm precipitation
types through the evening.

The eastern of the two lows is expected to move into Western
Prince William Sound Tuesday morning, which will help to spread
moisture over the Chugach and end the downsloping that has been
observed the past few days. However, the downsloping and advection
of warm air in the low to mid-levels has created an above
freezing layer between 1000 and 3000 ft. The 00Z Anchorage
sounding shows the wet-bulb temperature below freezing, so
precipitation will change over to all snow eventually should this
thermal profile maintain itself, but an hour or two of sleet or a
rain snow mix is possible early tomorrow morning before
precipitation saturates the column and switches to snow between
4am and 6am. Expect one to two inches of accumulation by noon
tomorrow for the Anchorage Bowl and two to four inches for the
Mat-Su Valleys.

Some uncertainty remains on Wednesday with models struggling to
resolve a shortwave rounding around a quasi-stationary low over
the Central Aleutians. More progressive model solutions bring
this wave over Southcentral while others keep it over Southwest.
This forecast package represents the westerly solutions which
maintain dry air over the Cook Inlet region. Regardless, broad
southerly flow will maintain precipitation over the Prince William
Sound Areas, with rain expected for Cordova and Seward and snow
likely from Girdwood to Whittier.

On Thursday, yet another low will move into the Western Gulf with
its front extending north to the Gulf Coast. In similar fashion to
the current system, precipitation will start out as snow with a
slow transition to rain for coastal areas later in the evening to
early morning hours on Friday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: This
afternoon through Thursday)...

Several weather disturbances will bring periods of light snow to
the region with only minor accumulations.

A weak upper level shortwave is currently moving through the area
with light snow reported across Bristol Bay, but only minor
accumulations expected. Another shortwave trough, which is
slightly stronger, will bring another round of snow to the area
tonight and Tuesday morning. Expect an inch or two of snowfall
across most populated areas by Tuesday morning. Temperatures will
also warm a few degrees each day as warmer air moves in from the
southeast. A stronger shortwave will push a warm front across the
area on Wednesday with a good chance of snow across many areas,
however some downsloping will develop west of the mountains and
lower precipitation chances in places like Iliamna and King
Salmon. Expect another 1 to 3 inches of snowfall across the area.
By Thursday a fairly strong low pressure system will move near
the south parts of the AKPen this will spread rain and snow to the
AKPen and near Dillingham, while areas near King Salmon and
Iliamna will experience a drier and warmer downsloping wind that
will keep this area drier on Thursday. Additionally, easterly
winds will increase across the area on Thursday ahead of the low
pressure system.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3:
This afternoon through Thursday)...

A cold front will continue to push across the southwest Bering and
western Aleutians tonight with cooler air and snow showers
expected. This will produce northeasterly Gales across parts of
the area through tomorrow. Meanwhile a persistent low pressure
just southeast of Nikolski while meander across the central
Aleutians through tomorrow with areas of Gales near the low. This
low pressure system will push a warm front across the eastern
Aleutians and AKPen Tuesday night and Wednesday with mostly rain
but some snow possible across the Alaska Peninsula where cooler
temperatures will be. Colder air will also move across the
northern and western Bering Wednesday and Thursday keeping the
threat of Gales and heavy freezing spray. Finally, a North Pacific
low will approach the Alaska Peninsula on Thursday with winds
increasing to Gales, but precipitation will be rain.

 &&

.MARINE (Days 3 through 5/Thursday through Saturday)...

Gulf of Alaska: A low near the Alaska Peninsula with warm air
advection will bring a front northward through the Gulf Thursday.
Gale force winds are possible as the front creates a barrier jet
along the coast and through Kamishak Bay through Thursday evening.
Gales could extend into Prince William Sound. Winds should
diminish Friday morning through Saturday. Another low will develop
and lift into the Eastern Gulf, elongating a trough that will
move into the Northern Gulf coast Saturday morning. Seas around 20
feet on Thursday evening subsiding slightly Friday and Saturday
to around 15 to 20 feet.

Bering Sea: A widespread area of gales and large
seas of more than 20 ft will sweep across the Bering/Aleutian
Chain starting Fri night through Sat night as a result of a strong
North Pacific low. The associated front from the low will usher
strong gap winds for the Aleutians and potentially strong gales
across Pribilof Islands by Sat night. Warm temperatures associated
with this system should minimize freezing spray risks over the
central Aleutians for the next few days.

&&

.LONG TERM FORECAST (Days 4 through 7/Friday through Monday)...

A low near the Alaska Peninsula area will move inland with an
associated trough northward towards the end of the week. Scattered
snow showers are possible for southwestern Alaska and periods of
heavy rain and snow spreading along the Gulf Coast from west to
east throughout the weekend. Out west along the Central and
Western Aleutians, a series of developing lows will usher in
periods of heavy precipitation throughout the weekend.
Precipitation could start as snow but expect any snow to
transition to rain. Brief, relatively quieter weather is possible
Monday for Southcentral.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Special Weather Statement: 125.
MARINE...Gales: 127, 130, 170, 173-178, 185, 411-414.
         Heavy Freezing Spray: 165, 185, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHCENTRAL ALASKA...CJ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RC
MARINE/LONG TERM...CB/VR