Gale Warning 777, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
422 AM AKST Fri Dec 11 2020

.ANALYSIS AND UPPER LEVELS...

An negatively tilted upper level ridge extending from the
Southwest to the Eastern Gulf persists through tonight. A
shortwave off a strong North Pacific low approaching the Southern
AKPEN early tomorrow morning will push the upper level ridge to
the east as it travels across the Southwest Coast. Thus,
Southcentral and inland Southwest should remain mostly dry over
the weekend. The deep low out in the Western Bering persists until
Saturday morning. The high amplitude trough extending south of
the Aleutians will pull a second strong system out of the North
Pacific towards the Southern AKPEN through tonight. This system
will cross into the Southern Bering on Saturday and absorb the
remaining surface energy from the Western Bering low as it
continues tracking northwest through the weekend. Another North
Pacific low approaches the Eastern Gulf on Sunday whose trough
will extend across the Gulf to Kodiak.

&&

.MODEL DISCUSSION...

Model agreement continues to improve for the North Pacific low
that will reach the Southern AKPEN by early tomorrow morning.
Track matches well across all solutions and general center
location is fair. The GFS does keep this system stronger than the
others through Saturday morning and 'catches up' to the others by
Saturday afternoon as the low continues to weaken. Models are
struggling with another deep North Pacific low approaching the
Eastern Gulf over the weekend. The main discrepancy is the NAM
forming a second low off the southeast coast of Kodiak Island on
Sunday. This is creating significant difference in winds down Cook
Inlet, along Eastern Kenai, and along the North Gulf Coast
compared to the other solutions.

&&

.AVIATION...
PANC...Low stratus and periods of fog will keep conditions at or
below marginal throughout the morning. Conditions should improve
back to VFR by this afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Through Saturday night)...

The main weather features are a series of low centers moving NW
across the Southern Gulf/NE Pacific. The first of these systems
heads north toward the AK Peninsula today and crosses into the
Bering Sea late tonight. This system will bring gales to the
Gulf waters today and tonight. Strengthening pressure gradients
associated with this low will also increase gap winds and general
offshore flow today and tonight. The associated front will spread
rain to Kodiak Island this afternoon and portions of the Southern
and Eastern Kenai Peninsula tonight and Saturday. The track of
the next low on Saturday is a little more uncertain as the models
differ on timing and position. These differences will affect the
northward extent of precipitation and timing of the winds. For now
it looks like the western Gulf will win out on both counts with
windy and raining conditions spreading across the area Saturday
and Saturday night. Winds will likely increase again across
portions of the north Gulf to Cook Inlet region with the brunt of
precipitation over the Western Gulf and Southern and Eastern
Kenai Peninsula.

Backing up some, stratus and fog over the Cook Inlet region to
the MAT-SU Valleys will break up some today and not likely reform
to a great extent tonight due to increased upper level cloud
cover and increasing winds. The stratus over the Copper River
Basin will be a little harder to move out as light winds and cold
temperatures will maintain stable continues across the basin.

&&

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

A negatively tilted upper level ridge will remain in place today.
Northeasterly surface flow will continue to bring cold
temperatures to the region, with highs only reaching the single
digits in the Kuskokwim Delta. A low will track into the eastern
Bering Saturday morning. Much of the associated precipitation will
remain offshore, however snow is likely for areas north of and
including Dillingham. Snow and blowing snow is also likely
Saturday afternoon along the Kuskokwim Delta coast. Another low
approaching from the Gulf on Sunday will bring more widespread
snow to the entire Bristol Bay region, with scattered snow
showers to the north. Significant accumulations are possible in
Dillingham by the end of the weekend, however uncertainty persists
as to where the heaviest snow will occur.

&&

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

A very active pattern will continue through the weekend.
Widespread rain/snow showers will persist across today associated
with a vertically stacked low over the western Bering. A strong,
compact low will track over the eastern Aleutians tonight,
bringing moderate rain east of Unalaska and easterly storm force
winds to Bristol Bay. It will continue to track northward
Saturday, leading to snow and blowing snow over the Pribilofs
before merging with the aforementioned low. This broad
circulation will continue to bring scattered rain/snow showers
through Sunday.

&&

.MARINE (Days 3 through 5/Sunday through Tuesday)...
A deep low over the Northeast Pacific will lift northward toward
the Gulf of Alaska on Sunday, but looks like it will stall just
south of the Gulf. Right now it looks like winds will top out at
small craft levels across the central to western Gulf waters, but
if the low does end up tracking a little farther north then would
expect gale force winds over the central Gulf.

Forecast confidence for the Monday through Tuesday timeframe is
low. The pattern looks favorable for fast moving deep lows, but
with a huge spread in model solutions it's impossible to say where
the lows will be located. Bottom line, gale force winds are likely
during this time period with a chance for storm force winds in
the vicinity of deeper lows.

&&

.LONG TERM FORECAST (Days 4 through 7/Monday through Thursday)...
The weather pattern next week looks quite dynamic, with a strong
subtropical jet stream over the North Pacific and a deep Arctic
low/trough somewhere over the Yukon and Mainland Alaska. There
will certainly be interaction between the northern stream and
southern stream energy. This pattern favors active weather across
the entire forecast area, with fast moving deep lows likely across
southern areas (the Aleutians eastward to the Gulf of Alaska). As
far as details on individual storms, it is impossible to say due
to the shear number and complexity of features. Stay tuned.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm: 130, 160, 165, 180
		 Gale: 131-132, 136-139, 150, 155, 178, 181, 185, 351-352, 414
	  	 Heavy Freezing Spray: 160, 181
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KM
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AP
MARINE/LONG TERM...SEB