Storm Warning 5, NWS Anchorage, AK

859 
FZAK61 PAFC 250003
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
303 PM AKST Tue Jan 24 2023

Offshore waters forecast for the Gulf of Alaska West of 144W

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ399-251430-
303 PM AKST Tue Jan 24 2023
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A front moves inland from the northern Gulf of Alaska for this evening.
A 994 mb North Pacific low at 52N 153W this afternoon moves to 58N 
149W at 992 mb for Wednesday morning. This low moves inland near 
Cordova at 1000 mb Wednesday afternoon. A weak surface trough moves 
from the western Gulf Wednesday afternoon to the northern Gulf for 
Thursday morning. 

$$

PKZ351-251430-
Gulf of Alaska Offshore North of 57N and West of 144W-
303 PM AKST Tue Jan 24 2023

...GALE WARNING THROUGH WEDNESDAY...

.TONIGHT...SE wind 15 to 30 kt becoming S 25 to 40 kt after
midnight. Seas 11 to 18 ft. Rain.
.WED...SW wind 25 to 40 kt. Seas 14 to 21 ft.
.WED NIGHT...SW wind 20 kt. Seas 11 to 15 ft.
.THU...W wind 10 to 20 kt. Seas 7 to 10 ft.
.THU NIGHT...SW wind 10 kt. Seas 7 ft.
.FRI THROUGH SUN...SW wind up to 15 kt. Seas 5 to 8 ft.

$$

PKZ352-251430-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
303 PM AKST Tue Jan 24 2023

...GALE WARNING THROUGH WEDNESDAY...

.TONIGHT...S wind 30 to 45 kt. Seas 12 to 20 ft. Rain.
.WED...SW wind 20 to 35 kt becoming S 15 to 25 kt in the
afternoon. Seas 13 to 21 ft.
.WED NIGHT...SW wind 20 kt. Seas 12 ft.
.THU...W wind up to 15 kt. Seas 7 to 10 ft.
.THU NIGHT...S wind up to 15 kt. Seas 7 ft.
.FRI THROUGH SUN...SW wind up to 20 kt. Seas 8 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
524 PM AKST Mon Jan 23 2023

.ANALYSIS AND UPPER LEVELS...
A low in the eastern Bering Sea is entraining bitterly cold air
from the interior of the state into Southwest Alaska today
bringing in a huge difference in temperatures between Southwest
and Southcentral today. Southwest Alaska is under arctic air with
temperatures remaining below zero over the Kuskokwim Valley and
Delta and single digits for Bristol Bay. Cross the Alaska/Aleutian
Range of mountains and temperatures jump into the 20s to 30s over
most of Southcentral. While this is a big difference, the real
airmass change is along the front extending from the eastern
Bering low and to the east. Temperatures to the south of this
front are in the upper 30s to 40s. This front can be seen on
satellite and moving northeastward over Kodiak and the Gulf of
Alaska. Far to the south of the Alaska Peninsula is a baroclinic
leaf that is where the low on Tuesday night/Wednesday will come
from which will be a major factor in the Southcentral weather.

&&

.MODEL DISCUSSION...
While models are in good agreement with each other the next few
days, they all are trending toward a slower and more easterly
progression with the features over Southcentral. Southwest Alaska
is more stable with run-to-run consistency. Of particular note is
the way the models are handling the low east of Kodiak Tuesday
night and moving over Prince William Sound on Wednesday. The
exact track of this low will be key to the precipitation type over
the various parts of the Kenai Peninsula and northward into
Anchorage and the Matanuska valley. This is a difficult situation
to forecast and therefore there may be significant changes to the
forecast between now and Wednesday morning for those areas
mentioned.

&&

.AVIATION...
PANC...MVFR conditions expected at time this evening then
becoming predominant VFR ceilings as southeast winds move over the
terminal. There is a threat for a freezing rain and snow mix this
evening before these southeast winds move in and warm temperatures
above freezing after midnight with rain. Winds will increase a
little more late Tuesday afternoon as precipitation ends and VFR
conditions prevail.

&&

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

An active weather pattern is expected to continue across
Southcentral through the short term forecast. A broad upper-level
trough stretches from the Bering Sea east to Southcentral with
various shortwaves embedded within the flow. These upper waves and
a warm surface front are tracking northward across Southcentral
and progressively bringing warmer air to the area. An increase in
southerly winds with the front will also promote warmer air to
spread into the region. As a result, temperatures are expected to
gradually climb above freezing and transition any snow to a wintry
mix or rain, from south to north. Freezing rain is also not out
of the question since any rain that falls onto cold surfaces could
freeze.

The transition from snow to rain is anticipated this evening into
tonight for the Western Kenai Peninsula northward into Anchorage
and the Matanuska Valley. Overall, accumulations are expected to
be light for these regions. Gusty southeasterly winds will also
begin to pick up this evening, particularity through Turnagain
Arm. The transition from snow to rain is expected to occur late
tonight into early Tuesday morning around Willow, and then Tuesday
afternoon for a mix of rain and snow in the Talkeetna area.
Farther north into the Susitna Valley, snowfall is expected to be
quiet heavy, with the highest snow accumulations over the Denali
State Park Area and moderate accumulations from the Talkeetna
cutoff north and west. A Winter Weather Advisory remains in effect
for these regions through Tuesday afternoon.

Precipitation continues into mid-week as a Gulf low extends its
front to the north Gulf coast by Wednesday morning. With this
system, a continued stream of warmer air would help keep
temperatures above freezing. Since the last forecast package,
however, model solutions have started to shift the low more to the
east, which would in turn create more precipitation type
headaches as slightly cooler air enters the equation.
Nonetheless, precipitation can be expected to continue for much of
Southcentral through Wednesday due to this low. Various upper
shortwaves will then maintain showery precipitation through the
first half of Thursday before a ridge builds across Southcentral
from the Gulf of Alaska.

&&

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

A ridge of high pressure over the Chukchi Sea and a low in the
Aleutians are currently driving an inverted trough over Southwest
Alaska. This is creating a favorable pressure pattern for strong
winds and persistent snowfall over Southwest Alaska. Looking
forward in the short-term, the trough will move westward out of
Southwest into the Bering overnight tonight, bringing the
strongest of the winds out of the area with it. The Blizzard
Warning that was issued for areas near Bethel, Kipnuk, and the
Kuskokwim Delta will be downgraded to a Winter Weather Advisory
for blowing snow and wind chills near -40F. The worst of the
conditions are expected to remain near the Kuskokwim Delta,
communities such as Kipnuk in particular.

Another wave of precipitation will move over the Alaska Peninsula
this evening. King Salmon will see a brief period of freezing
rain and ice pellets mixed with the snowfall in the evening hours.
This will transition to snow and some mixed precipitation before
midnight tonight. The wave will continue pushing northward
reaching the Kuskokwim Delta by early Tuesday morning. This
resurgence of snowfall to the Kuskokwim Delta is not expected to
cause a return to blizzard conditions, however blowing snow and
wind chills as previously mentioned will be present until the
morning Tuesday. Over the course of tonight, Tuesday, and Tuesday
night, King Salmon may see about an inch of new snowfall,
Dillingham 6-8 inches, and 1-3 inches in Bethel.

Offshore flow is expected to weaken Tuesday and Tuesday night.
Lingering snow showers across Southwest Alaska will also diminish
by Wednesday morning. As the trough over Southcentral weakens by
midweek, the pressure field that was promoting the active pattern
will have significantly loosened. However, a front approaching
from the Eastern Bering Sea looks to bring another round of active
weather to Southwest Alaska by Friday.

&&

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

A broad disturbed pattern persists across the Chain, driven by a
stark thermal boundary between the Eastern Aleutians and
Southwestern mainland Alaska. An associated steep pressure field
is driving gale-force northeasterly winds offshore from Mainland
Alaska, across the ice-edge into the Central Bering and partially
the Pribilofs. These winds have driven the reduced visibilities
due to blowing snow in the Pribilofs and conditions are now
expected to persist this evening and beginning to diminish by
midnight. Snowfall in the Pribilofs will continue until the early
afternoon Tuesday. The southernmost tip of the trough laid across
the Bering will dip into the Central Aleutians, continuing the
precipitation in the area through Tuesday afternoon. This trough
will then shrinkingly advance eastward toward the eastern
Aleutians, maintaining the rain and snow for this region through
Tuesday night.

Wednesday morning, a storm-force front will then move into the
Western Aleutians bringing Southerly winds and a leading band of
snow and mixed precipitation. Following the initial passage of the
front, a transition to rain is possible due to the warmer air
still entrained in the system. Southerly flow is currently
expected to continue following the passage of the front, leading
to mixed/rain lingering showers. The frontal boundary will advance
eastward steadily, reaching Nikolski by Friday morning.

&&

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

An active weather pattern looks to remain in place through the
weekend and into the early part of next week. On Friday, models suggest
a strong upper level ridge will build over the Gulf of Alaska and
southern Mainland. Meanwhile an upper level trough develops over
the far western Bering Sea and western Aleutians. There is growing
confidence that the building ridge over Southcentral will
introduce the potential for a warmup across the southern mainland,
but especially over Southwest Alaska this weekend as a surge of
warm southerly flow persists through most of the weekend.
Currently the 12Z GFS solution is an outlier, as it is the only
model showing the progression of an upper level trough from west
to east over the Alaska Peninsula late Saturday. If verified, this
feature would work to interrupt the warm southerly flow and bring
a brief period of colder air to Southwest. Conversely, the
EC/Canadian solutions do not show this progressive trough, and
instead keep consistent southerly flow in place over the eastern
Aleutians and Southwest Mainland all weekend. This type of setup
would bring a warm, wet, and windy pattern and would also
introduce the possibility of mixed precipitation.

Given these differences, confidence beyond Friday is low.
Typically when a strong upper level ridge sets up, it acts as a
blocking mechanism and steers all incoming troughs around it, so
still thinking the GFS is too quick to break down the ridge.
However, exact placement of the ridge and where the axis sets up
will be a determining factor too, as there could be differences if
the ridge builds slightly farther east. By Monday next week, the
ridge still looks to remain over the Gulf, while farther west, a
North Pacific low lifts northward into the western Bering, sending
a front across the Aleutian Chain and keeping the active weather
pattern in place.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY: 145 155 195.
MARINE...GALE WARNING: 119 131 176-178 185 411 412 414.
         HEAVY FREEZING SPRAY WARNING: 179 180 185 412 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...AF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CL
LONG TERM...KO