Gale Warning 277, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 PM AKDT Tue Mar 22 2022

.ANALYSIS AND UPPER LEVELS...

An omega blocking pattern continues to dominate the Bering Sea.
While upper level troughing dominates the western Aleutians and
western Bering as a front weakens as it moves underneath the
blocking high. Dry cold northerly flow dominates Southwest Alaska
with gusty north winds continuing from the Kuskokwim Delta towards
the AKPen. A deep trough extends across Southcentral into the Gulf
with a low pressure system moving across the central Gulf. This
low in the Gulf is producing snow and rain across the northern
Gulf with radar showing snow extending from Cordova to Whittier
with another band moving across the southern Kenai Peninsula.
Radar also shows a few stronger showers near Middleton Island as
cold unstable air aloft has produced a few lightning strikes
southeast of Cordova over the northern Gulf. Otherwise winds have
increased with the Gulf low with down inlet flow Anchorage to the
Cook Inlet have been experiencing north winds gusting up to 30
mph, as well as the Matanuska valley winds gusting up to 40 mph
and Gales across the northern Gulf as a barrier jet has formed.

&&

.MODEL DISCUSSION...

Models are in good synoptic agreement through Thursday as several
low pressure systems and shortwave troughs move across the Gulf
and into Southcentral. There are some small differences in the
placement of the low on Thursday east of Kodiak Island with the
GFS a bit farther south than most model runs. While models are in
good agreement with the blocking high over the Bering.
Temperature forecasts and p-types may be a challenge Wednesday
and Thursday afternoon due to the higher sun angle and breaks in
clouds. The western Kenai Peninsula, Anchorage Bowl and Matanuska
valley may see rain or a rain/snow mix if temperatures warm
enough. The other forecast challenge is the potential for blowing
snow across the southern AKPen as another shortwave enhances snow
showers and winds across the area Wednesday night into Thursday.
The winds may also be a bit tricky as there will likely be a brief
period of gusty Turnagain winds turning into Anchorage Wednesday
afternoon, and timing in the return of the Knik and other local
effect winds as stronger pressure gradient sets up by Thursday.

&&

.AVIATION...

PANC...VFR conditions will persist. Northerly winds will persist
through tonight with occasional gusts near 20 knot through this
evening and tapering off near midnight. There is a chance that
the terminal sees Turnagain winds from the southeast late
tomorrow afternoon.

&&

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

An onset into a more active pattern is expected over the next day
or so as a ridge out over the Bering moves north and closes off,
allowing a persistent area of low pressure over the Gulf to shift
west towards Kodiak Island and the Alaska Peninsula by Wednesday
morning. Snowfall will spread across the northern end of Kodiak
Island as the surface low moves nearly directly overhead tonight,
with around 3 to 4 inches of new accumulation possible for Kodiak
City before the low shifts west and weakens tomorrow morning.
Meanwhile, a series of easterly waves will move up around the low
into the Prince William Sound and Kenai Peninsula on Wednesday,
reinvigorating periods of snow along the eastern Kenai Peninsula
and Prince William Sound region. Gusty southeasterly winds will
develop across the Kenai Peninsula as a stronger trough axis
swings across by Wednesday afternoon, including through the Knik
River Valley and Turnagain Arm. The cross-barrier flow and
subsequent downslope warming/drying of the lower atmosphere
should keep most of Anchorage and the Mat-Su Valleys dry, although
a few sprinkles or flurries with showers moving off of the Chugach
Mountains can't be ruled out entirely.

Looking towards Thursday, another low is set to move into the
southern Gulf with it's attendant front moving up towards the
northern Gulf Coast through Thursday evening. A gale force barrier
jet will develop ahead of the front, with winds locally peaking at
storm force in the vicinity of Middleton Island early Thursday
afternoon. Steady onshore and upslope flow ahead of the front
will continue to support nearly steady snowfall along the western
Kenai Peninsula and Prince William Sound region on Thursday,
including Portage Valley, Girdwood and Turnagain Pass, where
between 1 to 2 feet of storm total snowfall is possible between
Wednesday afternoon and early Friday morning. A strong pressure
gradient between the Prince William Sound and Cook Inlet will
continue to drive gusty easterly winds across the Kenai Peninsula,
on Thursday, including through the Turnagain Arm and upper
Anchorage hillside. However, this should facilitate continued
downslope drying that will again prevent most if not all of the
heavier snowfall from reaching the ground over most of the MatSu
Valley and Anchorage areas.

&&

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

A fairly quiet pattern will continue across Southwest Alaska over
the next few days as dry offshore flow continues across the
region. Temperatures will moderate during this period as cloud
cover will increase and thus will allow for less outgoing longwave
radiation to escape into space. The best chance for precipitation
will be Thursday night into Friday morning across the Alaska
Peninsula and Bristol Bay as moisture wraps around the western
edge of a low in the Gulf. The best chance for precipitation will
be along the Alaska Peninsula as Ocean-Effect snow showers are
likely as cold air advection will persist across the eastern
Bering Sea. There is lower confidence with respect to the
intensity of these bands due to the ample ice cover across the
eastern Bering Sea which could limit convective snowband
development.

&&

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

An unsettled but fairly benign pattern will continue across the
Bering/Aleutians over the next few days. Small areas of low end
gale force winds are expected along a frontal boundary in the
central Bering/Aleutians through Thursday morning. Otherwise,
ample convective Ocean-Effect activity is expected due to strong
cold air advection across the Bering/Aleutians Wednesday and
Thursday. Ocean-Effect snowband activity will then decrease from
west to east on Friday as the cold air advection weakens.

&&

.Marine (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska: A storm force barrier jet along the northern Gulf
coast could linger into Friday morning. Winds should decrease
gradually in intensity during the day and throughout the weekend
as the associated low weakens. Highest seas following the barrier
jet up to 25 feet will begin subsiding Friday afternoon to less
than 10 feet after midnight and continue to subside into Sunday.
The placement of an approaching surface low to the western Gulf by
Sunday evening is not clear yet, but winds and seas may begin to
increase near Kodiak Island by the end of the weekend.

Bering Sea: Northerly flow begins to shift eastward through
Bristol Bay as a low to the west, just south of the Aleutian chain
continues east and its front potentially crossing into the
Bering. The extent northward into the Bering sea is a little more
uncertain. Low end gales are possible with the passage of this low
Friday into the weekend. Subsequently, higher seas up to 12 feet
with the frontal passage also remain uncertain with the northward
extent. By Sunday evening, another, more vigorous South Kamchatka
low approaches the most western extent of the Aleutians.

&&

.Long Term Discussion (Days 4 through 7: Saturday through Tuesday)...

A low approaches the western Gulf this weekend. Certainty in the
placement of this low and thus the chances and details for rain
and snow showers breaks down quickly Sunday and beyond. More
certainty exists for the AKPen and Kodiak Island for precipitation
this weekend into next week, however, the extent north into
southwest Alaska and eastward into southcentral on Monday morning
remains a little more unclear. Along the Aleutians, a brief ridge
of high pressure followed by a front approaching the western
extent Sunday night and progressing to the eastern Aleutians
through Tuesday. Temperatures trend warmer into the weekend and
then moderate until at least Tuesday when temperatures may
potentially nudge cooler Tuesday morning for southwestern Alaska.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 119 138 173 174.
		 Heavy Freezing Spray 160 179.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...AS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...VR