Small Craft Advisory 9, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
504 PM AKST Wed Jan 5 2022

.ANALYSIS AND UPPER LEVELS...

High pressure remains in place across the Yukon, extending west
across almost the entirety of mainland Alaska. A stalled out front
extending from the southern Gulf westward across all of the
Aleutians and southern Bering is acting as a train track for a
series of lows that are moving westward along that front.
Precipitation along the front is enhanced depending on where the
low is. Skies remain almost completely clear for the mainland
except along the Kenai Peninsula, and snow and rain continue at
times from Kodiak westward through to the AKPEN and Aleutians.

Gusty winds continue from the Matanuska Valley due to ongoing gap
winds to much of the Aleutians as a 968 mb low approaches Adak. An
easterly jet is following the Alaska Range and Kuskokwim Valley,
as ridging builds into the interior. The low approaching Adak is
vertically stacked.

&&

.MODEL DISCUSSION...

The models are in excellent agreement through Friday afternoon. A
few points of uncertainty really start from that point on. A wave
and front moving across the Alaska Range could re-up the winds a
bit through the Matanuska Valley Friday afternoon and evening.
While confidence is high that this event won't be nearly as bad as
the last one, it certainly adds insult to injury. The timing and
strength of the winds remain somewhat uncertain. Precipitation
types around the Aleutians remain a struggle as well as
temperatures hover near freezing across most of the chain. Overall
forecast confidence is high.

&&

.AVIATION...
PANC...VFR conditions continue. Winds will remain calm, generally
from the north. Next chance for precipitation expected Saturday.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 to 3)...

A upper level blocking pattern will keep conditions cold and
clear throughout mainland Southcentral until this weekend. Further
south over Kodiak and Middleton Islands, lingering snow showers
will begin to diminish later tonight, diminishing from east to
west.

As a low over interior Canada nudges a trough west Friday
morning, the arctic high pressure will elongate to the west enough
for the upper level gradient to increase a northerly jet over
South Central. Cold advection will follow behind and help
accelerate winds through many of the north to south wind prone
gaps on Friday, especially for areas near Thompson Pass, Valdez,
and the Copper River Delta. Areas further west, such as Broad pass
and the Mat Valley will be affected on Friday as well but the
peak winds will be later in the day Friday as a more substantial
trough sinks southward Friday night into Saturday. Wind chills
will decrease with this passage as winds increase late Friday,
particularly for the Copper River Basin and Thompson Pass.

Into Saturday morning, moisture will advect into the Prince
William Sound and eastern Kenai Peninsula and increase chances for
snowfall with notable accumulation across the Gulf coast and
Kodiak Island.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: Today
through Saturday)...

Weak zonal upper-level and surface flow will continue to bring
clear, cool, and dry conditions to the region. An upper-level
trough will descend from the north on Friday, which will slightly
cool temperatures as more arctic air is pulled south. Easterly
winds will also increase towards the end of the weak as a front
approaches the Aleutians and causes pressure gradients to tighten
over Southwest Alaska. No precipitation is expected for the work
week, but as the weekend approaches, a slight chance of
precipitation is possible over the Alaska Peninsula and Bristol
Bay areas.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3:
Today through Saturday)...

A vertically stacked compact low is currently tracking near the
western Aleutians. South to southeasterly flow wrapping around the
aforementioned low, extends eastward across the Chain and is
bringing predominately rain. The strongest easterly winds are
expected between Atka and Adak today and will diminish by early
Thursday morning. Rain/snow will reach the Pribilofs Thursday
morning and should tapper off by Friday. After a brief lull,
another series of lows will approach from the North Pacific by
Friday, leading to intermittent rain across the Aleutians into the
weekend.

&&

.MARINE (Days 3 through 5 - Saturday through Monday)...

Aleutians / Bering...Broad high pressure retreats to the Russian
Arctic by Monday. An elongated area of low pressure remains South
of the Aleutians, weakening over the Western Aleutians for Monday.
Forecast confidence decreases by the end of the period.
Widespread Easterly gales spread across the Aleutians and Bering,
becoming Northerly over the Central and Western Aleutians and
Bering by Monday. Seas building to 22 feet over the Bering Sunday
and Monday. Increasing risks for freezing spray over Western
Bering open waters through Monday. A North Pacific low moves
across the Alaska Peninsula Sunday to the Central Bering for
Monday.

Gulf of Alaska...A North Pacific low moves over the Alaska
Peninsula South of Kodiak Island Sunday. Forecast confidence is
mixed based on the low's track and timing. Gusty winds increase to
widespread high end gales with boundary jets storm force winds
along the Gulf coasts, diminishing late Sunday. Seas building to
22 feet over the Gulf for Sunday, subsiding Monday.Increasing
risks for freezing spray over open waters of Cook Inlet and
Kachemak Bay on Sunday.

&&

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

Looking ahead into the extended forecast, the latest operational
model runs are slowly coming into agreement with the evolution and
progression of the synoptic scale features for the weekend but
diverge in the specific details towards the end of the period. A
blocking ridge extending from the northern Bering Sea to eastern
Siberia will continue shifting westward on Sunday, while a trough
with an embedded low retrogrades westward across the Alaska
mainland and into the eastern Bering Sea. Meanwhile, this low will
eventually phase into a broader trough to the south of the
Aleutians, with increasing southerly winds drawing a deep fetch of
tropical moisture across the Bering into the Gulf. For Sunday
through Tuesday, models seem to key on a frontal boundary
extending from a center of a low, bringing precipitation from
Kodiak Island northward to the Alaska Peninsula, and into the
southern mainland. Where the uncertainty emerges is the track,
position, and timing of subsequent surface lows circulating
upstream of the main trough, but overall are trending toward a wet
and unsettled pattern to persist. Additionally, a tightening
pressure between the retreating high to the north and low pressure
in the Gulf will create conditions favorable for windy
conditions, especially through the gaps and passes. Increasing
moisture and cloudiness will also help with the much below normal
temperatures over the last several days to rebound across much of
the coastal areas and interior valleys.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory: 131.
MARINE...Gale Warning: 121, 127-128, 130, 132, 138, 150, 155,
		 165, 170-179, 185, 352, 411-414.
		 Heavy Freezing Spray Warning: 119, 121, 126-129, 139, 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...VR
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
MARINE/LONG TERM...KZ/MF

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