Gale Warning 3, NWS Anchorage, AK

182 
FZAK61 PAFC 030003
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
303 PM AKST Tue Jan 2 2018

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.

PKZ399-031430-
303 PM AKST Tue Jan 2 2018
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 999 mb low near 55N 149W will move to 60N 147W at 1000 mb late
tonight and then weaken inland on Wed. A ridge will build into the 
central Gulf Wed night. 

$$

PKZ351-031430-
Gulf of Alaska Offshore North of 57N and West of 144W-
303 PM AKST Tue Jan 2 2018

.TONIGHT...SW wind 10 to 20 kt. Seas 11 to 18 ft.
.WED...W wind 10 to 20 kt. Seas 11 ft.
.WED NIGHT...W wind 15 kt. Seas 8 ft.
.THU...W wind up to 20 kt. Seas 6 ft.
.THU NIGHT...W wind up to 15 kt. Seas 3 to 6 ft.
.FRI THROUGH SUN...S wind 20 to 35 kt. Seas 9 to 14 ft.

$$

PKZ352-031430-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
303 PM AKST Tue Jan 2 2018

.TONIGHT...W wind 10 to 20 kt. Seas 11 to 16 ft.
.WED...W wind 10 to 15 kt. Seas 10 ft.
.WED NIGHT...W wind 10 to 15 kt. Seas 8 ft.
.THU...W wind up to 15 kt. Seas 7 ft.
.THU NIGHT...SW wind 15 to 30 kt. Seas 6 ft.
.FRI THROUGH SAT...SW wind 25 to 40 kt. Seas 9 to 17 ft.
.SUN...SW wind up to 10 kt. Seas 8 to 12 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 PM AKST Mon Jan 1 2018

.ANALYSIS AND UPPER LEVELS...
A large mature low south of the Alaska Peninsula bottomed out
sometime early this morning around 961 mb and now is beginning
to slowly weaken as it lifts northward toward Bristol Bay. The
occluded and warm fronts are lifting northward out ahead of the
low with precip spreading inland across Southwest and Southcentral
Alaska. Strengthening easterly low level flow is leading to
downslope drying on the west side of mountain ranges, though
overrunning just out ahead of the strongest winds could produce a
brief period of very light precip. Much warmer air is also moving
in, leading to a transition to all rain along the coast. A nose
of warm air aloft is also spreading inland. Some of the strongest
winds with this system are behind the cold front and southeast of
the low center, coincident with cold advection and significant
pressure rises. These southerly storm force winds will begin to
make their way into the Gulf late this afternoon.

Out west, an upper level trough over the Bering Sea with broad
instability is producing snow showers, particularly over the
western to central Aleutian islands.

&&

.MODEL DISCUSSION...
All models show the same general synoptic idea, though there are
a bunch of differences with smaller scale features. In particular,
there are some differences in location and amplitude of upper
level waves traversing the southern Alaska mainland Tuesday night
through Wednesday night. Thus, confidence in the precipitation
forecast behind the big low drops significantly. This bears
watching, as one of these waves has the potential to produce
localized snow accumulation.

&&

.AVIATION...
PANC...Expect VFR conditions to dominate as east to southeast
downslope flow strengthens this evening through the overnight
hours. Surface winds will remain northerly, so there will be
periods of low level wind shear. As the low center makes its
way northward across Southwest Alaska early Tuesday, expect the
Turnagain Arm jet to bend into Anchorage, so southeast winds
will come up rapidly and remain gusty through Tuesday afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The frontal system currently over the northern Gulf will continue
north and inland spreading strong east to southeasterly flow
across southcentral Alaska tonight. With a moderately cold air
mass in place, precipitation inland will start as light snow,
however expect to see temperatures warming steadily as the
southeasterly winds strengthen. In areas such as the Anchorage
metro area, Eagle River and the Mat-Su valleys where downslope
warming will be strongest, expect the temperatures to climb into
the upper 30s late tonight and low to mid 40s tomorrow morning as
winds strengthen. The Copper River Basin is another location which
will likely see both strong southeast winds and a rapid warm up
as winds push into that area tomorrow morning. Along the coast
expect rain to continue to be heavy at times tonight through
Tuesday morning with significant new heavy wet snow in the
mountains above 1500 to 2000 ft.

In marine areas, widespread easterly gales ahead of the front
turning southeasterlies and the potential for a storm force
barrier jet over the north Gulf coast are the main initial
concerns. As a second wrap of the front moves into the southwest
Gulf tonight, southerly winds will increase to gales to storm
force winds in that area as well. In addition, the long southerly
fetch associated with this system will bring a rapid increase in
seas to the Gulf peaking between 30 and 35 ft.

Southeasterly flow will gradually diminish Tuesday afternoon and
evening and then rapidly drop off overnight. A weak frontal wave
will move north across the Gulf to the north or northeastern Gulf
Coast continuing precipitation over that area through Wednesday.
Elsewhere in southcentral, cold advection will slowly filter in
from the west, supporting isolated to scattered showers Tuesday
night and Wednesday transition from a mix of rain and snow showers
to predominately snow showers from west to east.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2...Mon and Tue)...
A surface low just south of the Alaska Peninsula moves to Bristol
Bay tonight pushing a broad front through the Kuskokwim
overnight. A mix of snow and rain will develop along the boundary
as it moves across Bristol Bay, with all snow expected as it moves
north across the Kuskokwim due to a colder air mass in place.
Precipitation tapers down late tonight, however it continues
through Tuesday night as the surface low weakens on a slow
northward track. A ridge pattern moves across the southwest for
Wednesday into Thursday creating drier conditions for mid week in
southerly flow. A cooler temperature trend is expected despite
south flow as cold air advects in from the Bering.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2...Mon and
Tue)...

Low pressure over the central Bering shifts south tonight and
slowly shears apart through Tuesday between the low pressure
lifting north across the Southwest and a ridge building into the
southwest Bering. This will give a brief break from gusty winds
through Wednesday morning, then the next North Pacific front moves
to the western and Central Aleutians. This storm system slowly
deepens on its northerly track to the western Bering. The
associated surface low strengthens from 970 mb to 960 mb as it
crosses the western Chain Wednesday afternoon. A triple point low
develops quickly during this time as another strong wave races
around the base of the storm system. Max gale force marine winds
are expected along the initial frontal boundary as it pushes
across, with precipitation quickly changing over to all rain along
this warm subtropical storm. The first frontal boundary pushes
across to the north and eastern Bering by Thursday afternoon. The
triple point low moves a re-enforcing gale force boundary to the
central and eastern Aleutians mid day Thursday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The long term forecast beginning Wednesday afternoon remains
progressive, as low pressure over the southern Mainland gives way
to an amplifying ridge building in from the west on Thursday. In
the meantime, a strong upper low will develop over much of the
Bering sea Thursday into Friday, then begin to push the above
mentioned ridge over the pan-handle and western Canada by the
start of the weekend. As the ridge builds into the southern
Mainland Wednesday into Thursday, cooler and drier conditions will
build back over the area under light offshore/northerly flow.

There is still some uncertainty regarding the finer details of the
complex north Pacific low and associated front tracking through
the Aleutians and into the Bering Wednesday into Thursday. This
is also true for the potent triple point low strengthening over
the north Pacific Thursday, then tracking through the Central and
Eastern Aleutians/Bering Friday. The associated front will reach
Southwest Alaska Friday morning and push eastward over much of the
southern Mainland by Saturday. Overall, this system will usher in
another round of wet and windy conditions for the much of the
area, as well as some warming temperatures ahead of the front as
the system progresses eastward.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale 120 125 129 136-140 150-160.
		 Storm 119 130-132.

&&

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...TP

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1201 AM AKST Tue Jan 2 2018

AKZ101-111-021515-
Anchorage-Matanuska Valley-
Including the cities of Anchorage, Eagle River, Indian, Eklutna,
Palmer, Wasilla, Sutton, and Chickaloon
1201 AM AKST Tue Jan 2 2018

...Areas of Freezing Rain through early Tuesday morning from
Anchorage through the Matanuska Valley...

Some areas of light freezing rain have developed around the
Anchorage area and is more persistent along the Glenn Highway
from northeast Anchorage through Eagle River up to Palmer and
Wasilla. This freezing rain is not expected to last very long,
but will keep roads slick through the Tuesday morning commute with
temperatures in places hovering around freezing. As temperatures
rise to above freezing Tuesday, the road conditions should
improve.