Gale Warning 692, NWS Anchorage, AK

619 
FZAK61 PAFC 311205
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
305 AM AKST Tue Dec 31 2019

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.

PKZ399-010300-
305 AM AKST Tue Dec 31 2019
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 974 mb low over Kodiak Island this morning will move up Cook
Inlet through Tue night at 973 mb then weaken through Wed night.

$$

PKZ351-010300-
Gulf of Alaska Offshore North of 57N and West of 144W-
305 AM AKST Tue Dec 31 2019

.TODAY...S wind 20 to 30 kt. Seas 15 to 18 ft.
.TONIGHT...SW wind 20 to 30 kt. Seas 15 to 19 ft. Snow showers and 
rain showers.
.WED...W wind 20 to 30 kt. Seas 16 to 24 ft. Snow showers.
.WED NIGHT...SW wind 15 to 30 kt. Seas 15 to 23 ft.
.THU...S wind up to 20 kt. Seas 9 to 14 ft.
.FRI THROUGH SAT...W wind up to 20 kt. Seas 4 to 7 ft.

$$

PKZ352-010300-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
305 AM AKST Tue Dec 31 2019

...GALE WARNING TONIGHT AND WEDNESDAY...

.TODAY...SW wind 20 to 30 kt. Seas 19 ft.
.TONIGHT...W wind 20 to 35 kt increasing to 30 to 40 kt after
midnight. Seas 17 to 25 ft. Snow showers and rain showers.
.WED...W wind 30 to 40 kt. Seas 23 to 29 ft. Snow showers.
.WED NIGHT...W wind 20 to 35 kt. Seas 14 to 27 ft.
.THU...SW wind 10 to 25 kt. Seas 8 to 16 ft.
.FRI THROUGH SAT...W wind 10 to 25 kt. Seas 7 ft.

$$

391 
FZAK61 PAFC 312352
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
252 PM AKST Tue Dec 31 2019

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.

PKZ399-011345-
252 PM AKST Tue Dec 31 2019
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 972 mb low over the Kenai Peninsula moves inland Tue night. A 
999 mb at 56N 157W Thu morning moves to 56N 155W at 997 mb Thu 
afternoon. 

$$

PKZ351-011345-
Gulf of Alaska Offshore North of 57N and West of 144W-
252 PM AKST Tue Dec 31 2019

.TONIGHT...SW wind 20 to 30 kt. Seas 15 to 19 ft. Freezing spray.
Rain showers transitioning to snow showers.
.WED...W wind 20 to 30 kt. Seas 16 to 24 ft. Freezing spray. 
Snow showers.
.WED NIGHT...SW wind 15 to 30 kt. Seas 14 to 22 ft. 
Freezing spray. Snow showers.
.THU...SW wind 10 to 25 kt. Seas 8 to 13 ft.
.THU NIGHT...E wind up to 20 kt. Seas 8 ft.
.FRI THROUGH SUN...W wind 10 to 25 kt. Seas 4 to 8 ft.

$$

PKZ352-011345-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
252 PM AKST Tue Dec 31 2019

...GALE WARNING THROUGH WEDNESDAY NIGHT...

.TONIGHT...W wind 20 to 35 kt increasing to 30 to 40 kt after
midnight. Seas 17 to 25 ft. Freezing spray. Rain showers
transitioning to snow showers.
.WED...W wind 30 to 40 kt. Seas 23 to 29 ft. 
Freezing spray. Snow showers.
.WED NIGHT...W wind 20 to 35 kt. Seas 18 to 24 ft subsiding to 12
to 20 ft after midnight. Freezing spray. Snow showers.
.THU...SW wind up to 20 kt. Seas 9 to 15 ft.
.THU NIGHT...S wind 10 to 25 kt. Seas 7 to 11 ft.
.FRI THROUGH SUN...W wind 10 to 25 kt. Seas 4 to 9 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 AM AKST Mon Dec 30 2019

.ANALYSIS AND UPPER LEVELS...
A polar front continues to dominate the weather across the Bering
Sea and Southwest Alaska as sub-500 dm 500 hpa heights remain in
place aloft. This very cold arctic air can be seen pouring out
over the Bering with a growing ice edge along the Kuskokwim Delta
coast. Widespread convective snow showers persist over the Bering,
with temps as cold as 9-13 degrees across the Pribilof Islands,
and -15 F and colder across the Kuskokwim Delta. On the east side
of the Alaska Range, warm subtropical air is advecting northward,
with a very pronounced subtropical jet stream associated with this
warm air advection regime. A leading low amplitude impulse aloft
is quickly propagating into Cook Inlet and the Kenai Peninsula
this morning, with the associated storm force front tracking
inland along the North Gulf Coast. This front has brought warm
southeast winds all the way into the Matanuska Valley, Prince
William Sound, the entire Kenai Peninsula, and the Anchorage
Hillside. Turnagain Arm was blowing hurricane force with 80 MPH
gusts at Mchugh Creek and 70+ MPH winds blasting over the
Hillside. There was even a report of 100+ MPH winds through the
upper Eagle River South Fork region above 3000 feet. Another
surface wave can be seen on satellite forming south of Dutch
Harbor, and this wave will rapidly amplify as the Bering Sea
potential vorticity anomaly aloft intersects it and moves into
Bristol Bay and across the Alaska Peninsula.

&&

.MODEL DISCUSSION...
The numerical weather models are all depicting a similar synoptic
pattern, and are in much better agreement with the overall
details of what is going to occur the next two days. However, some
finer and impactful details remain uncertain, with the first
being the westward extent of the deformation band snowfall across
Southwest Alaska. The GFS remains the farthest west with the heavy
snow band occurring from a north-south line from Dillingham north
to Sleetmute. The ECMWF and Canadian models are dramatically
farther east and favor a line from King Salmon to Sparrevohn. As
usual the extreme solutions are not favored so this forecast will
favor a middle ground solution, which is best depicted by the 00z
and 06z NAM.

For the remainder of the region, a powerful arctic front will
cross the AKPEN and lift north through Cook Inlet and and the
Gulf Coast Tuesday and Tuesday night. The NAM and hi res models
from the United States are clear outliers and would support a
snowstorm as the incredible cold air advection (-10 C at 850 hpa
in 3 hrs) would support a powerful front and heavy snow squalls
from the southern Kenai Peninsula northward to Anchorage. For
now, those solutions will be tossed, but they are duly noted.

&&

.AVIATION...
PANC...Light rain mixed with snow will end late morning, in
conjunction with light southerly winds. Expecting mostly VFR
conditions but CIGS will drop below 5000 feet at times. Expect
increasing low level wind shear this afternoon, remaining through
the TAF period.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The low currently over Cook Inlet will move north this morning and
dissipate by afternoon. This will bring a mix of precipitation
types to the area today with temperatures near freezing, except in
the central and western Copper River basin where they remain well
below freezing. Another system will push into the Gulf from the
southwest tonight and Tuesday. This will bring warmer temperatures
to the area. Precipitation will mainly be confined to the coastal
areas and the Susitna valley, with downsloping keeping the
northern Cook Inlet area fairly dry. The cold front with this
system will push through Kodiak Island beginning late Tuesday.
This cold front is quite vigorous and will bring dramatically lower
temperatures to the Island Tuesday night. The cold front will work
its way towards the Southcentral mainland Tuesday night.
The timing on this front is a little uncertain, but should push
across the Anchorage area late Tuesday night or Wednesday morning.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Another storm looks to affect the region, with the latest model
runs favoring a low pressure track from King Salmon to Anchorage.
With this in mind, the biggest change in the models has been to
shift the deformation band on the backside of the low further
east, with the heaviest snowfall now expected to be east of a
Dillingham to Crooked Creek line. Here, storm total snowfall
should be in the 10 to 25 inch range. As the low passes by, north
to northwesterly winds will increase with wrap around snowfall
continuing, allowing for fairly widespread blowing snow to
develop. Most locations will see visibilities reduced to less than
one mile at times as the heavy snow, light powdery nature of
snow, and increasing winds all interact.

Further west across the upper Kuskokwim Delta, this region will be
well removed from the snowfall, but will also be in line to see
the cold air advection aloft kick in the fastest, with 850 mb
temperatures dropping below -30 C. By tonight, sustained winds of 20
mph, with gusts at or above 30 mph, will be common during the
overnight hours. This will create dangerous wind chill conditions,
with the previous forecast package having issued the wind chill
advisory. Overall, not much change for this region as our previous
thinking remains on track. The cold weather will continue on Tuesday
area-wide, with snowfall decreasing from southwest to northeast as
we head into the evening.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
As an area of low pressure passes by to the east, a reinforcing
shot of cold weather will drop south across the Bering and
Aleutians. This will maintain an active snow shower pattern, some
of which could be locally intense, as the ocean delta-Ts increase
(the temperature difference between the sea and roughly 9000
feet). This pattern looks to continue through Tuesday.

&&

.MARINE (Days 3 through 5)...
(Tuesday through Thursday)

...Bering Sea and Aleutian Coastal Waters...

Northerly gales and seas 15 to 25 feet will continue across the
eastern half of the Bering and Aleutians on Tuesday as low
pressure south of the AKPEN moves toward Kodiak Island. For the
western Bering, winds and seas will relax as a ridge builds over
the region. The gales diminish in coverage on Wednesday as the
low enters the Gulf and the ridge expands eastward over the
central Bering. By late Wednesday into Thursday, a band of
southeasterly gales will develop ahead of a front moving over the
Western Bering and Aleutians.

...Gulf of Alaska...

Broad southerly small-craft level winds, with perhaps some
embedded gales, will persist across the Gulf on Tuesday as a front
lifts toward the Southcentral coast. An area of westerly gales
will expand across the western and southern Gulf late Tuesday
into Wednesday as the low south of the AKPEN lifts toward a
position near Kodiak Island. These winds will continue into Thursday
as the low tracks in the northern Gulf. Seas will range from 15 to
25 feet across the Gulf through late Thursday before diminishing the
low tracks toward the Alaska Panhandle.

&&

.LONG TERM FORECAST (Days 3 through 7)...
(Tuesday through Saturday)

The active weather pattern that has been so persistent for well
over a week now will continue into the new year. By Tuesday, the
main weather feature will be a 960 to 970 mb low spinning up in
the north Pacific south of the eastern Aleutians with yet another
arctic trough digging south over the Bering. As has been the case,
model performance this far out has varied considerably. Thus,
confidence in the evolution of this surface low and its
interaction with the digging trough remains low. With that said,
it does appear that this system will bring accumulating snow and
strong northeasterly winds to portions of Southwest Alaska. The
main difference between the models is track and timing, and these
variables will impact where the heaviest bands of snow set up.
Right now, this could be anywhere from along the Alaska Range
north to Bethel.

For Southcentral, Tuesday will also be quite active as a series of
shortwaves ahead of the aforementioned low ushers in bands of
precipitation and much warmer air with a continued southerly
flow. It is hard to believe right now with so much cold air in
place, but this system looks to push temperatures above freezing
not just for the immediate coast, but also for areas farther
inland and around Cook Inlet. Obviously, any mention of
temperatures above freezing will mean a changeover in
precipitation from snow to a wintry mix or even all rain. The big
question remains how much of this precipitation makes it over the
mountains and into places like Anchorage, as there will also be a
downslope component accompanying these shortwaves which will help
limit precipitation amounts. The warmer temperatures and mixed
precipitation will continue into Wednesday as the main low tracks
into the Gulf.

Conditions then turn colder and more showery for the second half
of the week as the low tracks south and a ridge develops over
interior Alaska. This set up will usher in colder air across the
Southern Mainland as northerly outflow winds pick up in intensity.
By the weekend, it appears the Southern Mainland will remain cold
and fairly dry. The active weather will stay over the Bering and
Aleutians where a series of surface fronts attached to a Kamchatka
Low pass over the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning 155 161.
 Winter Weather Advisory 181.
 Wind Chill Advisory 155.
MARINE...Gale Warning 150 155 160 165 170>173 175>177 179>181 185.
 Heavy Freezing Spray 160 165 179>181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JA
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
MARINE/LONG TERM...CK/SB