Gale Warning 586, NWS Anchorage, AK

864 
FZAK61 PAFC 030039
OFFAER

Offshore Waters Forecast
National Weather Service Anchorage AK
339 PM AKST Mon Nov 2 2020

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.

PKZ399-031415-
339 PM AKST Mon Nov 2 2020
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...

A 993 mb low persists near 59N 144W through Tue, then dissipates 
Tue night. A 999 mb low will track from Bristol Bay to 56N 152W 
Tue night, then exit into the Pacific on Wed.

$$

PKZ351-031415-
Gulf of Alaska Offshore North of 57N and West of 144W-
339 PM AKST Mon Nov 2 2020

.TONIGHT...W wind 15 to 30 kt. Seas 7 to 12 ft.
.TUE...NW wind 15 to 30 kt. Seas 5 to 10 ft.
.TUE NIGHT...NW wind 15 to 30 kt. Seas 6 to 9 ft.
.WED...NW wind 10 to 20 kt. Seas 4 to 7 ft.
.WED NIGHT...NW wind 15 to 30 kt. Seas 6 to 11 ft.
.THU THROUGH SAT...S wind 15 to 30 kt. Seas 6 to 11 ft.

$$

PKZ352-031415-
Gulf of Alaska Offshore South of 57N North of 55N and West of
144W-
339 PM AKST Mon Nov 2 2020

.TONIGHT...NW wind 10 to 25 kt. Seas 9 to 13 ft.
.TUE...NW wind 15 to 30 kt. Seas 10 ft.
.TUE NIGHT...W wind 15 to 30 kt. Seas 6 to 9 ft.
.WED...NW wind 15 to 30 kt. Seas 5 to 10 ft.
.WED NIGHT...NW wind 15 to 30 kt. Seas 7 to 12 ft.
.THU THROUGH SAT...S wind 15 to 30 kt. Seas 9 to 14 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
456 PM AKST Sun Nov 1 2020

.ANALYSIS AND UPPER LEVELS...

A strong and very cold area of high pressure persists across
interior areas of Southcentral and Southwest Alaska this afternoon.
The cold air draining through the gaps with a strong low over the
eastern Gulf is causing strong gap winds through Thompson Pass
this afternoon, with winds increasing across the Matanuska Valley
as well. High Wind Warnings are in effect for tonight in these
same areas. Incredible amounts of dust can be seen on satellite
coming out of the Copper River Delta on the strong winds. Several
lake-effect/ocean effect snow bands are over the far southern Cook
Inlet, moving over Kodiak Island with a new one forming over the
southern Cook Inlet on northeast winds. Fog developed over Bethel
this morning and will likely persist near the area through the
afternoon. A front and associated low are over the North Pacific
just south of Adak, with the front stalled just south of Adak,
paralleling the Aleutians.

In the upper levels, a positively tilted low and associated trough
are located over the Matanuska Valley this afternoon, extending
over the rest of Southcentral southwest through Kodiak. Ridging
is building over the western Bering, with a second vertically
stacked low over the North Pacific south of Adak.

&&

.MODEL DISCUSSION...

Model agreement is excellent on the large scale through Tuesday
afternoon. Thus, forecast confidence is very high. The magnitude
of the peak winds tonight in Thompson Pass and the Matanuska
Valley remain the primary forecast challenge, along with the
potential for blizzard conditions Tuesday afternoon and evening
across the Kuskokwim Delta.

&&

.AVIATION...
PANC...VFR conditions will persist. Gusty northerly winds have
developed and will persist from now through much of the day on
Monday.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3...Today
through Wednesday)...

A very cold air mass combined with a strong polar upper level wave
will continue to move through Southcentral this afternoon through
early Monday before stalling across Prince William Sound. The
upper level low will remain stalled through Tuesday afternoon
before finally moving off to the east. This combined with the
very cold air mass and high pressure across the ALCAN border
will create a tight pressure gradient across Southcentral. As a
result, gusty northerly winds are expected across the Anchorage
Bowl through Monday night with the peak winds occurring later
tonight into early Monday morning. Peak wind gusts are expected to
be anywhere between 30-40 mph, especially West Anchorage near the
airport. Winds will gradually diminish through Monday night and
into Tuesday as the upper level low pulls away and the pressure
gradient eases. Southcentral will remain precipitation free
through the next three days with loads of sunshine.

A High Wind Warning remains in effect for the Thompson Pass area
from now through 9 AM Monday morning for sustained winds of 45-60
mph and wind gusts as high as 75 mph. On the east side of the
polar low, there really isn't any upper level forcing. Thus,
counting on tightening surface pressure gradients as low headed
fro Southeast Alaska gets a little closer. It's also possible
winds may end up being a little weaker. Winds ease some Monday
but will remain gusty over the next three days as the cold air
remains in entrenched across the Copper River Basin and pressure
gradients remain relatively tight. Also, there is the slight
chance that some very light snow might try and make it into the
Thompson Pass and Cordova region Monday afternoon through early
Tuesday as a weak low develops south of the Copper River Delta.
Very dry low level air in place will work against this, so the
better chance for snow will be along the coast.

The High Wind Watch previously in effect for the Matanuska Valley
has been upgraded to a High Wind Warning as of earlier today.
Expect sustained winds of 35-45 mph with wind gusts as high as
65 mph beginning around 6 PM this evening and continuing through
9 AM Monday. Winds will gradually diminish during the day Monday
but will remain gusty through Tuesday.

&&

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

A ridge of high pressure over the Bering Sea will continue
interacting with a low in the Gulf of Alaska and bring a steady
offshore wind flow this evening and tonight. Winds are expected to
be stronger tonight than they were last night, making for a less
favorable environment for fog. GOES-17 Day Snow-Fog RGB shows that
nearly all the fog in the Kuskokwim Delta has cleared and moved
offshore. Monday will be a fairly quiet day weatherwise as this
offshore flow continues. A shortwave trough will move in from the
northwest on Tuesday bringing snow to the Kuskokwim Delta. There
is high confidence that temperatures at the surface and aloft will
remain cold enough that all precipitation will fall as snow.
Behind this shortwave, conditions look ideal for Ocean-Effect
Snow. Temperatures between the surface over the Bering Sea and
850mb will differ by at least 13-15 degrees Celsius with
northwesterly flow. The strong cold air advection will keep the
boundary layer coupled and promote instability for convective
snowbands to form. A Winter Storm Watch has been issued for
Tuesday afternoon through late Tuesday night as wind gusts are
expected to exceed 35 mph with visibility of 1/4 miles or less
possible. The heaviest snow and lowest visibilities will be near
the coast, though inland areas (including Bethel) will also see a
period of gusty winds and falling and blowing snow.

As the short-wave continues southward, expect solid gales along
the southwest and Alaska Peninsula coastal waters. Expect the
typically stronger winds through gaps of the Alaska Peninsula,
likely reaching storm force. This air mass is impressively cold
for this time of year and will allow freezing spray to spread
south of the Alaska Peninsula, which is pretty rare for early
November.

&&

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

A fairly quiet weather pattern is in store for the Bering/Aleutians
this evening and tonight as high pressure moves over the area,
causing winds to ease. This quiet weather will continue on Monday
but will be short-lived as a shortwave trough moves across the
eastern Bering on Tuesday. Due to the strong cold air advection
behind the front with brisk straight-line northwesterly flow,
Ocean-Effect snow showers are expected across the eastern
Aleutians and across the AKPEN Tuesday evening through late
Wednesday morning. A front will enter the western Bering/Aleutians
Tuesday evening and bring gale force winds to the area. The front
will continue eastward Tuesday night, bringing storm force winds
to the western Bering/Aleutians late Tuesday night into Wednesday
morning.

&&

.MARINE (Days 3 through 5/Wednesday through Friday)...

Northwesterly gales and seas 10 to 15 feet will persist across
the Bristol Bay and AKPEN marine zones Wednesday before
diminishing Wednesday night. There could be storm force gusts
along the south side of the AKPEN.

A Kamchatka low will sweep a front with southwesterly storm-
force winds and seas to 30 feet over the western Bering/Aleutians
by Wednesday. These winds will move east along with the front to
the AKPEN and eastern Bering/Aleutians by Thursday with storms
diminishing to gales and seas of 15 feet. Westerly gales will
continue behind the front over the Bering through Thursday before
diminishing to widespread small-craft level winds and waves by the
end of the week.

For the Gulf, northwesterly gales with seas to 10 feet are likely
to linger through Thursday from the Barren Islands to Shelikof
Strait. Gusty northerly outflow winds will also likely continue
into Thursday along the immediate Southcentral coast. These winds
are expected to diminish by the end of the week.

&&

.LONG TERM FORECAST (Days 4 through 7/Thursday through Sunday)...

The long term forecast begins Thursday with an eastward
progression of the upper-level trough-ridge pattern that has
dominated the weather over the past few days. This shift is due to
a deep arctic trough digging south across west Asia amplifying
the pattern and shifting the ridge that has been over the western
Bering/Aleutians toward the AKPEN and the trough over the state
toward Canada. At the surface, this translates to the cold surface
ridge sitting along the AL-CAN border slowly tracking into the
Yukon and Northwest Territories by the end of the week. As it
does, the pressure gradient between it and the trough over the
northern Gulf will relax allowing the strong outflow winds across
coastal Southcentral to wind down. The decrease in northerly flow
will also allow temperatures across the Southern Mainland to
slowly warm back up.

Farther west, a storm-force Kamchatka low looks to sweep a front
toward the AKPEN and Southwest coast by Thursday. An increasing
southwesterly flow will usher in warmer air that will allow
precipitation along the front to transition quickly from snow to
rain along the coast. Farther inland, precipitation looks to
remain all snow or a wintry mix as the front pushes onshore and
quickly weakens by early Friday. Models are also indicating the
potential for a triple-point low to spin up along the now weakened
occluded front somewhere near Kodiak Island. This solution would
help enhance a moist, southerly flow over the Gulf and spread
light snow across Southcentral Alaska for Friday as the surface
low quickly tracks east over the northern Gulf.

A second trough looks to move over the Kuskokwim Delta by
Saturday with another round of light mixed precipitation for
Southwest Alaska as the southwesterly flow continues due in part
to the now stationary aforementioned Kamchatka low. Models then
begin to diverge more significantly by Sunday regarding a north
Pacific low moving toward the AKPEN. Previously, guidance
indicated the potential for this system to lift due north over the
AKPEN into the eastern Bering. Recent runs, however, have moved
away from this solution toward one that would bring this system
closer to the AKPEN then drive it east over the Gulf. This
solution would still bring some rain, snow, and stronger winds to
the AKPEN and Bristol Bay late Saturday into Sunday, especially as
it interacts with the trough moving over the Kuskokwim Delta. The
greatest uncertainty is centered around the track of this low as
it enters the Gulf and whether any precipitation and/or gap winds
develop over the southern half of Southcentral Alaska by the end
of weekend and into early next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning 111 131.
MARINE...Storm Warning 131.
   Gale Warning 120 121 125 127 128 130 132 136 139 140 176 177.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...MV
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...TM