Gale Warning 165, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
649 PM AKST Wed Feb 9 2022

.ANALYSIS AND UPPER LEVELS...

A positively tilted, upper-level low currently centered over
Hooper Bay remains nearly stationary this afternoon. This feature
is responsible for the intrusion of a very cold arctic airmass
over Southwest Alaska and almost the entirety of the Bering and
Aleutian Chain. A series of shortwave troughs are rounding the
base of the trough and moving toward the east-northeast, guided by
the southwesterly upper-level flow between the low and an upper-
level ridge extending across the Canadian Rockies.

The first of these troughs is moving over the Copper River Basin
with an associated surface low weakening as it moves northeast
from the Northern Gulf toward Cordova. Areas of snow continue from
Valdez to the Copper River Basin were a light northerly flow near
the surface has brought temperatures back down into the 20s. Snow
showers are also falling across Cook Inlet north to the Mat-Su
Valleys in the wake of the surface low.

The second trough is over Bristol Bay and is moving east. This
feature will help to push the arctic air over Southwest, and
reinforce the cold air advection currently taking place over
Kodiak Island and the southern Cook Inlet. For Kodiak City and
Homer, westerly winds are gusting to 35 mph. Snow showers and
blowing snow is also occurring around the Homer area.

The third shortwave is extending across the Pribilofs and is
keeping snow showers going across Saint Paul Island. This feature
will help spin up a surface low that will move toward Bristol Bay
this evening. Farther west, colder air spilling south continues to
produce clouds and snow showers for the western Bering while and
area of low pressure in the North Pacific is moving north and
pushing higher clouds over the Central and Eastern Aleutians.

&&

.MODEL DISCUSSION...

Models are beginning to come into better agreement with the
complex surface low with multiple centers moving northward
towards the Aleutian Islands and Bering Sea this evening through
Thursday. The NAM/EC/GEM all depict the first of these centers
just south of Adak/Atka Thursday morning with a front positioned
south of the Pribilofs. The 18z NAM is now hinting at a weaker
surface low farther south and west. The GFS is also farther west
with this low, with both models now shifting the core of heaviest
precipitation west of the Pribilofs. The position of this feature
will also determine if and when warmer air does work in across the
Central Aleutians and whether snow switches over to rain.

Models are also struggling with the potential of a triple point
low spinning up along front lifting toward the AKPen late
Thursday. If this low does develop, as the GFS and NAM are hinting
at, there could be stronger winds through Shelikof Strait and the
gaps and passes along the coast. Models are in better agreement
with moisture spilling over Bristol Bay for Friday as the
front/low moves northward.

&&

.AVIATION...

PANC...MVFR conditions are expected with temporary IFR conditions
through Wednesday evening as bands of light snow continue to move
over the terminal. MVFR conditions are expected to lift back to
VFR conditions later this evening as the system passes and snow
diminishes. Light southwesterly winds this afternoon will give way
to gusty southerly winds that will lingering through early
Thursday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Saturday night)...

Skies are beginning to clear as the surface low moves inland.
Most of the lingering snow will slowly taper off into the evening.
A few additional inches of snow are possible as an upper level
low pivots eastward through the night. Shortwaves transiting
around this upper level low will favor light snow accumulations
along the west- and south- facing mountain slopes of the Talkeetna
and Kenai ranges.

Thursday remains fairly quiet until a North Pacific low pushes its
front into Southcentral Thursday afternoon through Friday
morning. Confidence is increasing with the track of this low,
though some uncertainty remains with the timing of its front.
Precipitation will favor the North Gulf Coast and Eastern Kenai
Peninsula, and will likely remain all snow except for Kodiak and
parts of Eastern Prince William Sound.

Some areas in Prince William Sound will see little break in
precipitation as a third system moves across Bristol Bay and
towards Southcentral Friday afternoon. Much uncertainty remains
with the track of this third low and how far inland precipitation
will spread. For now, precipitation looks to remain primarily
along the North Gulf Coast, with some upsloping along mountains
further inland. If the low remains weak, typical downslope areas
along the Kenai Peninsula and Anchorage Bowl could see some snow.
Meanwhile, persistent snow over Eastern Prince William Sound could
produce snow totals approaching a foot through Saturday afternoon.

&&

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

An upper low over Norton Sound combined with its upper trough over
Southwest AK will continue to bring steady light snow and increased
clouds east across much of Southwest AK tonight into Thu morning.
A strong upper high from the Gulf making its way over Southern AK
Thu morning will force the upper low to retreat further north Thu
afternoon. Meanwhile, a North Pacific low pushes its way through
Bristol Bay starting Thu afternoon into Fri morning, bringing warm
southwest winds and rising temperatures for much of the Alaska
Peninsula and Bristol Bay in the lower 30s to upper 30s between
Thu and Fri. Along the ridging axis, mostly clear and cooler
temperatures will be found underneath it as the ridge moves
northeast until it exits the Southwest Fri night.

Overall, a round of rain/snow mixed is expected especially along
the Bristol Bay and the Alaska Peninsula the next couple days,
with mostly light snow farther inland of the region through the
long term.

&&

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

The Winter Storm Watch for the Pribilof Islands has been upgraded
to a Blizzard Warning this evening. 4 to 6 inches of snow
are expected in response to a strong frontal system expected to
pass through Thu morning through Thu evening. Meanwhile, a North
Pacific low south of the Central Aleutians will bring gales and
warmer temperatures across the Bering/Aleutians starting tonight.
This system will then rotate across the Western Aleutians Fri
morning, causing the area of widespread gales to shift westward
and farther away from the forecast zones Fri evening. Winds will
linger over the Central to Western Aleutians Fri night into Sat
morning. Overall, strong gap winds and elevated seas will continue
over much of the Bering and around the Aleutian Chain for the
short term.

&&

.Marine (Days 3 through 5: Saturday through Monday)...

Gulf of Alaska:

A North Gulf Coast low moves inland and dissipates for Sunday.
Gusty southwest winds over the Gulf diminish Sunday. Seas to 12
feet subsiding. A second low moves across the southern Gulf with
gusty northwest winds through Monday. A new low and front
approach the southwestern Gulf with increasing southwest winds
on Monday.

Bering Sea/Aleutians:

High pressure moves into the eastern Bering for Monday. Forecast
confidence uncertain with approaching North Pacific low. The
Aleutian low complex merges with the approaching low. Widespread
easterly gusty winds with areas of gales over the Central
Aleutians increase to become widespread high end gales with areas
of storm force winds ahead of the front moving over the Aleutians
and Bering. Seas to 20 feet extend across the Aleutians into the
Bering through Monday. There is a risk of freezing spray over the
open waters of the western Bering.

&&

.Long Term Discussion (Days 4 through 7: Sunday through Wednesday)...

The first couple days of the long term period (Sunday through
Tuesday) remain in fairly good agreement on the large scale upper
level pattern across southern Alaska. Models depict a strong
North Pacific ridge remaining anchored in place during this time
frame with brief extensions of it northward into the Bering Sea
and southern Alaska. They also keep an upper level trough
anchored across the North Slope and the Northwest Territories
during this time frame. Another stronger and closed off upper
level low remains in place south of the Western Aleutians.
Basically, expect occasional systems of various strength and size
to move up and over this ridge breaking it down some from time to
time. This will result in occasional rain/snow for Southcentral
with any rain mostly being confined to the coastal areas and
Kodiak Island where warm air will more easily move in. For Tuesday
night through Wednesday, model guidance starts to spread out on
how the upper level pattern will evolve with the EC being most
robust with the upper level trough over the North Slope extending
southward especially across Southcentral Alaska. The Canadian-NH
and the GFS remain more modest with this keeping the overall
pattern earlier on in the period in place with periodic rounds of
precipitation. Overall, models keep temperatures in the normal to
slightly above normal area during this time frame.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Avalanche Warning: 131.
		 Blizzard Warning: 195.
MARINE...Storm: 119 120 138.
Gale: 125 128-137 139 141-165 175-177 179 180 351-414.
Heavy Freezing Spray: 121 129 130 138 139 141 179 185 412 414.

&&

SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHCENTRAL ALASKA...KC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...KZ/MV