Gale Warning 831, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
432 PM AKST Sun Dec 18 2022

.ANALYSIS AND UPPER LEVELS...

The upper level ridge over Southwest Alaska through the Bering
Strait has retrograded a little allowing a slightly stronger
northerly gradient aloft over Southcentral Alaska today. This is
helping to increase the northerly gap winds and spin up a surface
low near Middleton Island which can be seen especially well on
visible satellite.

Farther west, stratus remains over the interior Kenai Peninsula
as can be seen on the Daytime snow-fog band from the GOES
satellite. The gap winds through the Matanuska River Valley are
not strong, but have been enough to locally break up the
inversion over Wasilla and raise temperatures to 10 to 15 above
while Palmer and Big Lake are below zero or struggling to reach
zero this afternoon.

Southwest Alaska is clearing out today though there is some north
winds as well which are dropping wind chill reading to well below
zero such as near Bethel. Temperatures over the Bering Sea are
rather warm due to the warm ridge over the region. Cold Bay and
Dutch Harbor are caught in the frontal band between this ridge and
a low in the western Aleutians. bringing wind and rain to these
areas.

&&

.MODEL DISCUSSION...

Overall model agreement is good over the synoptic-scale, but there
are a few areas that should be looked at a little closer. The
biggest area of uncertainty is in the north Gulf coast just south
of Prince William Sound tonight through Tuesday. Models agree on
there being a low but low strength and especially track is quite
different which will impact winds and snowfall around the Prince
William Sound region of the early part of the week. There is also
some discrepancy on the way numerous weak lows develop and move
along a frontal boundary across the Alaska Peninsula through
northwest Bering Sea during the mid-week period. Models are in
good agreement with the front itself which is a more significant
feature, but some of the forecast for the Bering Sea may be
adjusted due to these lows.

&&

.AVIATION...
PANC...There is a chance for fog to develop again overnight.
However, due to the increased northerly winds, it looks like it
would be more of the periods of fog moving in and out variety and
not long-duration fog.

&&

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

An amplified ridge of high pressure, extending down into the
Alaska Peninsula from Arctic Russia, will begin to retreat
northward over the next 24 hours as troughing over Yukon begins to
expand into Southwest Alaska through Tuesday. Generally clear
conditions are forecast across Southcentral through Monday, though
the usual threat of fog will exist in the low lying areas and
beneath the upper inversion. A colder air mass also continues to
filter into Southcentral from the Alcan border and should allow
for continued subzero overnight lows for the region. Glennallen
dropped below minus 30 degrees last night and will likely do so
again tonight. Anchorage will be "warmer" and in the minus single
digits. Winds through Thompson Pass will remain gusty with wind
gusts of 40 to 50 mph possible through Monday night.

Some question marks with the forecast begin to arise over the
next 24 hours with the evolution of a small low pressure center
into the northern Gulf on Monday. Model agreement has been poor,
but this area of low pressure could bring snow into Cordova and
the Eastern Chugach Mountains on Tuesday. A frontal system then
looks to cross the Alaska Peninsula Wednesday on approach to
Southcentral. Kodiak could see a mix of rain and snow while
coastal areas further north would likely not see precipitation
impacts until early Thursday.

&&

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

A fairly quiet, cold and dry weather pattern will continue across
Southwest over the next few days as offshore northeasterly flow
persists. Offshore flow will be strongest on Wednesday, especially
in coastal areas along the Kuskokwim Delta and Bristol Bay.

&&

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

A fairly active weather pattern is expected over the next few days
as low pressure moves in from the North Pacific. This low will
bring widespread gale force winds across the central and eastern
Bering/Aleutians Monday through Wednesday. Widespread storm force
winds are expected across the central Bering Sea on Wednesday.
Rain will also accompany this low across the Pribilof Islands and
Aleutian Islands. Temperatures will be warm enough for the
dominant precipitation type to be rain. As temperatures cool on
Wednesday, precipitation is likely to turn to wet snow at the end
across the Pribilof Islands before tapering off.

&&

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

A blocked, high amplitude ridge dominates over western Alaska
through the eastern Pacific. Offshore flow and bitter cold
temperatures prevail for inland Alaska going into midweek. The
trough sinking south across Alaska early in the week appears to
stall midweek and become elongated and stretched through the
Bering while the eastern Pacific ridge remains stubborn to
breaking down. Couple this with a large area of cyclonic flow over
the Aleutians and an enhancement of strong easterly winds look to
span across the Gulf and into the eastern Bering. The Bristol Bay
area and the Alaska Peninsula could have especially gusty winds
and a broad swath of precipitation Thursday.

Cold air drainage may continue through the rest of this week as
cold air sits over the interior. Any enhancement to the pressure
or temperature gradient could help to accelerate air through wind
prone gaps over Southcentral and near the Gulf coast.

A similar repeat in this pattern is possible going into next
weekend. A Canadian trough sinking south and stretching west into
the Bering. The challenges under this synoptic regime is whether a
low will suppress the eastern Pacific ridge enough to bring a
system to the Gulf. It appears possible at the end of the week.
There is still a lot of uncertainty associated with the synoptic
pattern during this timeframe. The track of any low east could be
blocked and progression of a low could be bumped north or west.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 119 127 155 170-172 179 185 411-414.
		 Heavy Freezing Spray Warning: 139 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
LONG TERM...VR