Gale Warning 644, NWS Anchorage, AK

183 
FZAK61 PAFC 210015
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
315 PM AKST Tue Nov 20 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.

PKZ399-211345-
315 PM AKST Tue Nov 20 2018
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...
A 987 mb low near 59N 146W will remain nearly stationary and weaken
into a trough by Wed night. A developing 994 mb low near 54N 147W
Tue evening will move to 54N 135W at 985 mb Thu afternoon.

$$

PKZ351-211345-
Gulf of Alaska Offshore North of 57N and West of 144W-
315 PM AKST Tue Nov 20 2018

.TONIGHT...W wind 10 to 20 kt. Seas 5 to 9 ft.
.WED...W wind 10 kt. Seas 6 ft.
.WED NIGHT...N wind 10 kt. Seas 6 ft.
.THU...N wind up to 15 kt. Seas 5 ft.
.THU NIGHT...NW wind up to 15 kt. Seas 4 ft.
.FRI...S wind up to 15 kt. Seas 4 ft.
.SAT THROUGH SUN...SE wind 10 to 25 kt. Seas 12 to 18 ft.

$$

PKZ352-211345-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
315 PM AKST Tue Nov 20 2018

.TONIGHT...W wind up to 15 kt. NW wind increasing to 25 kt west of 
150W after midnight. Seas 6 to 9 ft.
.WED...NW wind 10 to 25 kt. Seas 6 to 10 ft.
.WED NIGHT...NW wind 10 to 20 kt. Seas 6 to 9 ft.
.THU...NW wind 10 to 20 kt. Seas 5 to 9 ft.
.THU NIGHT...NW wind up to 20 kt. Seas 5 ft.
.FRI...S wind 10 to 25 kt. Seas 4 to 8 ft.
.SAT THROUGH SUN...S wind 10 to 25 kt. Seas 12 to 20 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
441 PM AKST Mon Nov 19 2018

.ANALYSIS AND UPPER LEVELS...
A vertically stacked, occluded low can be spotted spinning over
the western Gulf of Alaska this afternoon. It lies at the base of
an extended trough over Southwest Mainland Alaska with the main
upper level low near St Matthew Island. Southcentral Alaska
remains in the warm sector of this system, but the whole airmass
is moderating due to the low being occluded. Temperatures aloft
are generally colder in Southwest Mainland Alaska and the Bering
Sea. A secondary trough extends out of the low near St Matthew
Island to near Adak where a surface low is increasing the pressure
gradient in the Central and Eastern Aleutians.

&&

.MODEL DISCUSSION...
Models remain in good synoptic agreement through much of the
week. The only real item of note is Wednesday night through
Friday with the complex low moving just south of the Aleutians.
The models have the same track of the low overall, but there is a
considerable spread in where the individual low centers that make
up the complex move. This is mainly an issue for the Aleutian
Island forecasts as the remainder of the area will be north of the
complex low and therefore will not be affected much by the
development and movement of the individual centers.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. There may be
enough clearing overnight to allow some fog back into the area
tonight due to an abundance of surface moisture with recent rain
and above freezing temperatures. However, conditions overall are
not terribly favorable to widespread fog with the upper level
trough overhead and some mid and high level clouds over the
region.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The surface low currently in the Gulf, south of the Kenai
Peninsula will track slowly to the northeast tonight through
Tuesday to be located just off of Cape Saint Elias by Tuesday
evening. The low will then turn to the northwest and gradually
fill and then dissipate as it drifts towards Prince William Sound
through Wednesday. A cold upper level low will track from
Southwest Alaska over southern Kodiak Island Wednesday evening and
then continue southeastward into the far southern Gulf through
Thursday. In response to the upper level low, a cold and drier
air mass will filter into Southcentral Alaska Wednesday and
Thursday, bringing decreasing clouds and increase offshore flow.

&&

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

Areas of light snow will develop from Bristol Bay north through
the YK Delta tonight as a strengthening trough slides onshore and
lifts north over St. Mary's. Tomorrow, a secondary area of low
pressure will move onshore along with the associated mid-level
trough. This will usher in another round of snow showers from the
Kuskokwim Delta south to Dillingham. Accumulations will be on the
light side, with less than an inch expected in low-lying areas
and an upwards of a couple of inches for the Kilbuck Mountains
and Nushagak Hills. Farther south, an area of low pressure
currently south of the Pribilofs will bring a mix of rain and snow
for the AKPEN overnight through Tuesday as its tracks southeast.

As the mid-level trough and associated surface feature move south
and east tomorrow, much colder air will begin to spill south
along the coast. The steeper lapse rates from the cold air
advection combined with the sheared upper-level trough aloft will
help enhance snow shower activity through early Wednesday. The
bulk of these snow showers will fall directly along the coast and
north-facing slopes of the Aleutian Range. The trough continues
to move south and east Wednesday as a mid-level ridge develops
over the interior. Clearer and drier conditions prevail for much
of the southwest Tuesday night through Thursday as the ridge
settles over the interior, providing a cold offshore flow.

&&

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

A strengthening area of low pressure south of the Pribilofs will
move east toward the AKPEN tonight with a trailing cold front
sweeping eastward. This system will bring widespread precipitation
along the eastern Aleutians and AKPEN with sustained small-craft
winds over the southern Bering and areas of gales along the
Pacific side of the chain. High pressure will develop over the
central Bering tomorrow as the low moves across the AKPEN. Brisk
northerly winds and scattered snow showers will also develop over
the eastern Bering Tuesday and linger through Wednesday as colder
air advects south between the high and the departing low.

Farther west, another occluded front with widespread
precipitation and weak gales will track over the western
Aleutians late Tuesday night, reaching the central ALeutians late
Wednesday. A triple-point low will then develop south of Adak
Wednesday night and move north into the Bering for Thursday.
As it does, its associated warm front will swing across the
eastern Aleutians and southern AKPEN.

&&

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

The long-term forecast remains an uncertain one during the Friday
through Monday time frame. While all the models have a good handle
on day 4 of it being seasonably cold and quiet across mainland
Alaska, the uncertainty develops behind where a strong low
tracking eastward along the Aleutians goes, how strong it gets,
and how quickly it moves. Each of the models has a different
solution to this. As a new low over the north Pacific approaches
it, the low is expected to deepen as the two lows merge. The GFS
and EC both keep the low drifting eastward, while the Canadian
tracks it faster into the Gulf. In addition, there is significant
uncertainty by Sunday and Monday as to exactly where the cold air
sets up, with the GFS by far the warmest, the Canadian the
coldest, and the EC in the middle. Most of the models agree the
seasonably cold and quiet weather for Thanksgiving and Friday
turns warmer and wetter by the weekend over Southern mainland
Alaska, but how much so remains a question with significant
uncertainty.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales...130 131 132 174 178.

&&

SYNOPSIS AND MODEL DISCUSSION...AH/EZ
SOUTHCENTRAL ALASKA...JR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM
LONG TERM...JW