Storm Warning 25, NWS Anchorage, AK

676 
FZAK61 PAFC 180013
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
313 PM AKST Fri Feb 17 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.

PKZ399-181445-
313 PM AKST Fri Feb 17 2023
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 998 mb low at 59N 140W exits into Southeast Alaska Sat morning. A 
999 mb low forms over Kodiak City Sat morning and moves to Prince 
William Sound at 999 mb Sat afternoon then to 60N 144W at 1012 mb 
Sun afternoon.

$$

PKZ351-181445-
Gulf of Alaska Offshore North of 57N and West of 144W-
313 PM AKST Fri Feb 17 2023

...GALE WARNING SATURDAY AND SATURDAY NIGHT...

.TONIGHT...SW wind 15 to 30 kt becoming SE late. Seas 11 to 19 ft. 
Rain.
.SAT...SW wind 20 to 35 kt increasing to 40 kt in the afternoon.
Seas 11 to 19 ft.
.SAT NIGHT...W wind 40 kt. Seas 15 to 20 ft.
.SUN...W wind 20 to 30 kt. Seas 12 to 15 ft.
.SUN NIGHT...W wind 15 to 30 kt. Seas 9 to 13 ft.
.MON THROUGH TUE...NW wind 15 to 30 kt. Seas 9 to 14 ft.
.WED...SW wind 10 to 20 kt. Seas 6 ft.

$$

PKZ352-181445-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
313 PM AKST Fri Feb 17 2023

...GALE WARNING THROUGH SATURDAY NIGHT...

.TONIGHT...S wind 20 to 35 kt. Seas 13 to 18 ft.
.SAT...SW wind 35 kt. Seas 15 to 20 ft.
.SAT NIGHT...W wind 25 to 35 kt. Seas 13 to 19 ft.
.SUN...W wind 15 to 30 kt. Seas 9 to 15 ft.
.SUN NIGHT...W wind 15 to 25 kt. Seas 10 ft.
.MON THROUGH TUE...NW wind 15 to 30 kt. Seas 9 to 17 ft.
.WED...SW wind 20 kt. Seas 7 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 PM AKST Thu Feb 16 2023

.ANALYSIS AND UPPER LEVELS...

The jet stream continues to pull in moisture from the south with a
deep trough over the western Bering and Aleutians. This jet
stretches from the eastern Aleutians supporting a deepening low
near the central Aleutians which is producing gales and areas of
storm force winds. Behind this low, in the colder air,
instability showers are occurring over the western Bering and
Aleutians. The jet then moves across the AKPen into the Gulf as it
crosses a broad ridge over the Gulf. A weak shortwave is moving
across Southcentral producing areas of light snow mainly over the
Susitna valley. Otherwise, onshore flow is producing snow showers
across Prince William Sound.

&&

.MODEL DISCUSSION...

Models continue to be in decent agreement with synoptic scale
features, but are still disagreeing with the finer details.
However, the models are coming into a bit better agreement with
the occluded low moving into the Kuskokwim Delta on Friday but
still some small differences on where it moves onshore, the
challenge this presents is where the strongest core of winds will
arrive onshore tomorrow morning. Additionally, a triple point low
develops across the western Gulf, models are coming into a bit
better agreement with this feature and are trending southward
towards the GFS solution. Another low pressure system moves out of
the northern Pacific Friday night taking a similar track to the
last low but a little farther east with the low tracking into
Bristol Bay on Saturday morning. Models are in better agreement
with this feature compared to previous model runs. If this track
continues the strongest winds are expected from near King Salmon
and south across the AKPen. Another triple point low forms near
the Kenai Peninsula along the next front moving into the Gulf
Saturday associated with the parent low across Bristol Bay. The
models are tracking this triple point low near the east coast of
the Kenai Peninsula and up into Prince William Sound but there is
still some model spread on solutions.

&&

.AVIATION...
PANC...A shortwave producing very light snow and lower ceilings
will continue to produce MVFR conditions and will persist through
the afternoon becoming VFR by late afternoon or early evening.
Another frontal system will move towards the airfield with steady
light snow developing tomorrow morning with MVFR to IFR
conditions expected. Snowfall is expected to be around 2 to 3
inches before ending in the afternoon.

&&

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

The jet stream curves north into the Gulf, guiding two storm
systems into Southcentral Alaska for Friday and Saturday. For
tonight, upslope snow showers continue along Southern Mainland
mountains as a negatively tilted upper level shortwave moves east
across the region. More active weather is present near Kodiak
Island, where a low near the Pribilof Islands is beginning to push
a front into the Western Gulf. Expect conditions to deteriorate
through the afternoon and evening for Kodiak Island as the front
brings light to moderate precipitation, with snow early in the
event transitioning quickly to rain.

As the front continues trekking eastward through tonight, a
triple point low will develop near the Barren Islands. Pressure
gradients tightening around this new low will help set the stage
for strong easterly winds through Eastern Kenai Peninsula and
Turnagain Arm late tonight into tomorrow morning. A Winter Weather
Advisory remains in effect for Eastern Kenai Peninsula as
moderate to heavy snow falling in conjunction with gusty winds
could lead to reduced visibilities and hazardous driving
conditions. Aside from gusty winds along the Anchorage Hillside,
winds should remain much lighter for the remainder of Southcentral
with this event. Snow amounts will also be much lighter outside
Eastern Kenai Peninsula, with about 2 to perhaps 5 inches expected
from Friday morning through early afternoon. Forecast confidence
is moderate to high, with the biggest uncertainty involving the
timing of snowfall.

After a brief break Friday evening, a very similar second system
is on tap for Southcentral. There remains some uncertainty with
the strength and track of this second triple point low, but
forecast confidence is steadily increasing. Much of the
precipitation is expected to fall as snow along Prince William
Sound, with little accumulation expected in the interior due to
downsloping and the quick progression of this system through and
out of Southcentral. As the low departs east for Sunday morning,
expect skies to begin clearing and gusty offshore winds to take
hold.

&&

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

A deepening low in the eastern Bering Sea will approach the
Southwest coast this evening, pushing its front inland through
Friday morning. Winds increase this evening as the front
approaches, with snow moving in from south to north tonight.
Blowing snow will reduce visibility across the Kuskokwim Delta
and Bristol Bay, for which Winter Weather Advisories remain in
effect through Friday morning. Snow totals with this system will
range from 3 to 6 inches broadly across Southwest Alaska, with
greater localized amounts possible. The bulk of this snow will
accompany the front Thursday night, clearing out of Bristol Bay by
morning, ending the blowing snow threat. As the low moves inland
over the Yukon-Kuskokwim Delta, winds will shift out of the
southwest and are expected to reach gale force along the coast.
Winds gusting as high as 50 mph will be possible through the day.
Lingering snow showers wrapping the low center are expected to be
widespread enough across the Kuskokwim Delta for blowing snow and
low visibility to stick around into Friday afternoon. Winds will
ease Friday evening as the low exits to the north.

For Friday, a second strong and compact low is expected to take a
track to the east of the first low. This low will push its front
into Bristol Bay Friday night, bringing another round of snow and
strong winds to the area. This is likely to lead to another
period of low visibilities from blowing snow through Saturday.
There is still significant uncertainty with the low track, which
could place its center anywhere from Cape Newenham to near
Dillingham. This leaves an open question as to how much snow the
Kuskokwim Delta will see as a result. The front may creep
northward enough to bring several inches of snow, though some
models keep the area mostly dry. The potential for blowing snow is
variable along with this. Saturday night, the low tracks inland
and snow tapers from west to east along with it. Colder, drier air
moves in as the low exits to the northeast for Sunday, as a
transient ridge brings in calmer conditions.

&&

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

A broad longwave trough remains situated over the western Bering
Sea, with a large low pressure system at its center just north of
the western Aleutians. It extends its front eastward across the
Bering Sea, where a compact triple point low is developing this
afternoon. The low will bring precipitation and strong winds to
the eastern Aleutians/Bering Sea, including the Pribilof Islands.
The low center looks to track just east of the Pribilof Islands
this evening before lifting toward the Southwest coast. A second
compact triple point low spins up along the central/eastern
Aleutians. This low has the potential to bring a core of strong
southwesterly winds to the eastern Aleutians. Hurricane force
gusts are likely to be associated with the low along the south
side of the system. However, where this corridor of strong winds
ends up is sensitive to the low track, with which there remains
some uncertainty. There is even some indication that there are two
different centers of cyclogenesis. While the western feature is
favored to be dominant and more likely to bring strong winds to
the eastern Aleutians, if the eastern feature wins out this would
keep the strongest winds south of the Alaska Peninsula. By
Saturday, the low moves inland over Southwest Alaska, leaving the
Bering under the influence of a broadly uniform cold air mass,
allowing for a period of showery, relatively benign weather this
weekend.

&&

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

The long-term features higher confidence that a frontal system
will move through the central Bering Sea/Aleutians during the day
on Monday. This front will eventually move through Southwest and
Southcentral Alaska Monday evening through the day on Tuesday.
There are some model differences in the strength of the front, but
the overall synoptic idea remains consistent.

A broad upper-level ridge in the Bering Sea builds in behind the
frontal system as it progresses eastward to Southeast Alaska and
Canada. This ridge is poised to move over Southwest and
Southcentral Alaska starting on Tuesday and lasting through much
of the long-term into Thursday. While deterministic guidance and
ensemble guidance generally have agreement with the evolution and
progression of this ridge, confidence lacks at this time if there
will or will not be waves of energy traversing around the
periphery of the ridge (a dirty ridge). Thus, confidence is also
low on the tracks/positions of any potential shortwaves traversing
the ridge periphery. Currently The GFS/CAN/ECMWF ensemble suites
as well as the ECMWF deterministic guidance depict more of a clean
ridge with little in the way of shortwaves moving around it. The
GFS/CAN deterministic guidance do advertise more in the way of a
dirty ridge with various weak shortwaves rotating around its
periphery. This will be something to monitor as details become
clearer with time.

Confidence is increasing for a period of quieter weather for
Southcentral Alaska Tuesday through Thursday with the ridge axis
moving overhead. Meanwhile, after a break from active weather late
Monday and through Tuesday, Southwest Alaska re-enters moist
southwesterly upper-flow with precipitation chances returning
Wednesday through the rest of the long-term. The Bering Sea and
Aleutian Chain, particularly the western and central
Bering/Aleutians will continue to remain active through the long-
term with persistent troughing overhead and a number of North
Pacific Lows and fronts lifting northward into the Bering through
the long-term.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 125 155 161.
MARINE...Gale 119 120 130-132 137-139 150-179 181 185.
		 Storm 180.
	 	 Heavy Freezing Spray 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...KC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CQ
LONG TERM...DN