Gale Warning 14, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
506 AM AKST Sun Jan 16 2022

.ANALYSIS AND UPPER LEVELS...

An upper level low is currently moving across Southcentral with
the center moving across the northern Kenai Peninsula this morning.
This upper level low was responsible for bringing much of
Southcentral the fresh snowfall yesterday. NWS Anchorage recorded
a snowfall of 2.5" from this past event bringing the snow depth up
to 16". Overall, from the storm reports we received it looks like
there was anywhere from 1 to 2 inches on the northern Kenai
Peninsula near Kenai/Soldotna to Sterling, 2 to 4 inches across
the Anchorage Bowl with 3 to 6 inches on the Anchorage Hillside
and Eagle River. Similar amounts to the Anchorage Hillside and
Eagle River were generally reported for the Matanuska Valley from
this event. All of the snow has virtually come to an end across
the Kenai Peninsula and Anchorage Bowl with some partial clearing
for these areas. Talkeetna and Skwentna in the Susitna Valley as
well as Palmer to Wasilla were still reporting some light snow
overnight as the upper level low continues moving eastward. Snow
was also falling across eastern Prince William Sound including
Valdez for much of the night. Cordova was mostly rain for much of
the event but observations after midnight show a rain/snow mix
falling. Temperatures area-wide are once again mostly in the 20s
with a few pockets of low 30s. Copper River Basin remains the cold
spot with temperatures ranging from single numbers to as high as
the upper teens near Paxson, though, Gulkana has a stratus deck
nearby but temperatures were still staying below zero. Kodiak was
observing mostly clear skies and temperatures around freezing.

Southwest Alaska remains fairly quiet with some snow showers
continuing mainly across the Lower Kuskokwim Valley as the
upper level low continues transiting eastward. Bethel was
reporting some fog though this has had not impact on the
visibility as of this writing. Temperatures across Southwest
mostly range from teens to 20s with the 20s more so over Bristol
Bay and south along the Alaska Peninsula.

A storm force low continues spinning south of the Aleutian Chain
this morning with its front slowly moving northward through the
Bering. Shemya observed 55 knot winds yesterday with the front as
it pushed through. The front is now bringing Dutch Harbor gusty
southeasterlies this morning with easterly winds increasing for
the Pribilofs as the front approaches. Cold Bay was also observing
increasing southeasterly winds this morning of 15 to 25 kts so
far. Heavy freezing spray continues along the ice edge southwest
of Saint Matthew Island as winds remain northeasterly.

&&

.MODEL DISCUSSION...

Models remain in overall great synoptic agreement out through Sun
night. Models begin to diverge on an upper level shortwave that
will be moving northward from the North Pacific towards the
Central Aleutians late Sunday night and into Monday morning. The
NAM seems to be the outlier on this upper level shortwave showing
a more concentric and closed off upper level low while the
GFS/Canadian-NH/EC keep it an open wave/open upper level trough as
it moves northward into the Bering. They also disagree on the
placement and timing of the evolution of this shortwave as it
moves eastward through Tuesday. Therefore, this will have sensible
weather impacts as it moves along the Eastern Aleutians to the
Alaska Peninsula. Also, believe it or not, models are in better
agreement on a secondary upper level shortwave that will round the
base of the trough Monday through Monday night. At the surface,
models are also in decent agreement on a surface low developing
and moving northwestward to somewhere south of Shemya Tue morning.
Models all agree that this upper level shortwave will
absorb/phase with the energy of the current storm system spinning
there but disagree on the timing with how fast this process will
occur. For Southcentral, while model guidance mostly agrees on the
upper level pattern, determining how clear areas will get or if
there will be fog/low stratus were the forecast challenges this
forecast package. In turn, this will impact the temperature
forecast as well.

&&

.AVIATION...

PANC...VFR conditions are expected to persist through around
17/02z. After 17/02z, expecting ceilings to lower as the afternoon
progresses coming down to IFR ceilings. Expecting IFR ceilings for
for most of the overnight time frame, though, LIFR ceilings are
possible over the terminal. Expecting any LIFR/IFR ceilings to
slowly rise Monday morning back to VFR conditions, though, this
may be a slow progression. Light southerly winds will become
northerly this afternoon and remain northerly through the
remainder of the TAF package.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Tuesday night)...

A large upper level low sitting over Southcentral this morning
will exit slowly eastward through the day. Some snow showers
will linger through the morning hours, but expect little or no
additional accumulation. Offshore flow, subsidence, and tight
pressure gradients on the back side of the low will lead to some
localized gap winds along the coast, namely for Seward/Resurrection
Bay, Whittier/Passage Canal, and the Valdez coastal waters. These
winds will be short-lived, dying down tonight as a ridge of high
pressure builds over Southcentral and the Gulf.

Cooler temperatures will settle in across the region today through
tonight. However, areas of low clouds will persist and limit how
much temperatures drop. The most likely areas for low clouds to
settle in include northern Cook Inlet, northwestern Kenai
Peninsula, Anchorage, and the southern Mat-Su. Weak northwest
flow behind the exiting low will push remaining low level
moisture/clouds up against the west side of the mountains.
Secondarily, expect low clouds in the Copper River Basin, where
partial clearing has already led to some areas of stratus early
this morning. As the upper ridge builds overhead tonight,
subsidence aloft will increase leading to increasing stability
in the low levels. Thus, would expect areas of fog to form,
especially where there are light winds and breaks in the clouds.
Once again, the northern Cook Inlet region and Anchorage area
seems the most likely to see fog. There won't be any big changes
to the atmosphere until Tuesday, so fog and low clouds will
linger.

The upper level ridge will gradually shift eastward Monday night
through Tuesday night, allowing systems to approach from the
south and west. Initially, these features look pretty weak. While
confidence is not high, it looks like a series of short-waves will
track across the western Gulf/Kodiak Island Monday night-Tuesday
and continue into Southcentral Tuesday afternoon-Tuesday night.
Light snow is likely as these move through. A warm front moving
up from the Pacific will lead to a changeover to rain on Kodiak
Island sometime Tuesday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today through
Monday night)...

A lobe of enhanced vorticity extending off an elongated upper-
level low moving across Southcentral continues to support light
snow showers over the Lower Kuskokwim Valley this morning. Snow
will taper off through the morning hours as the upper low exits
eastward and is replaced by a shortwave ridge. Southwest Alaska
begins to dry out, at least in terms of precipitation, as this
ridging overspreads the region today. Low stratus will continue to
linger, with a few pockets of clearer skies, before a front
moving north from the Bering begins to impinge on the Southwest
coast on Sunday night. Only a light dusting of snow is now
expected from this system, with the heaviest accumulations, around
half an inch, expected along the Kuskokwim Delta coast. Snow
amounts decrease quickly to zero inland.

Monday night into Tuesday, another front begins to push
northward across the eastern Bering into Southwest Alaska. A
compact upper-level low drives northward in tandem with the
front, lending potential for this next round of snow to be more
impactful.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Today
through Monday night)...

A strong frontal system connected to a North Pacific low will
continue to be the main weather driver for the Bering and
Aleutians through the short term. Gales arc along the front north
of the Aleutians this morning, with a swath of storm force winds
north of Attu. The Pribilofs also see snow today as the front
pushes north, turning to rain tonight as precipitation begins to
taper off. Various weak lows race northward across the Aleutians
as they circle the larger, deeper low center off the western
Aleutians, inducing intermittent periods of gustier winds and rain
showers. Rain and gusty southerly winds push into the eastern
Aleutians later this morning and reach the AKPEN by tomorrow
morning. Throughout the forecast period, a persistent swath of
northeasterly gales is present over the north and western Bering
as it produces heavy freezing spray conditions.

&&

.MARINE (Days 3 through 5 - Tuesday through Thursday)...

Gulf of Alaska...High pressure moves onshore over Southeast
Alaska for Wednesday. A well developed low enters the Western Gulf
Wednesday and moves to the North Gulf Coast by Thursday. Its
front extends across the Gulf through Thursday. Forecast
confidence is good. Gusty winds spread over the Gulf, increasing
to Easterly gales Wednesday, diminishing Thursday. Seas build to
15 feet Wednesday, subsiding Thursday.

Aleutians / Bering...A well developed low South of Amchitka
retrogresses South of Kamchatka for Thursday. Forecast confidence
is mixed with the low's movement. Broad low pressure remains in
place South of the Aleutians and Alaska Peninsula through
Thursday. Arctic high pressure holds over the Russian Far East.
Widespread gales extend across the Central and Western Aleutians
and Bering. Seas to 22 feet, subsiding from East to West by
Thursday.

&&

.LONG TERM FORECAST (Days 4 through 7: Wednesday through
Saturday)...

Latest model guidance is in reasonable agreement with the
evolution and progression of synoptic scale features into early
next week. However, models begin to diverge significantly with the
specific details towards the end of the period. For most of the
southern mainland, high pressure will give way to a brief period
of dry weather and seasonal temperatures before a wet pattern
returns Wednesday and onward. There is decent consistency for a
North Pacific low tracking south of the Alaska Peninsula into or
near the Gulf, with another low following closely behind later
next week. Models are keying in on a frontal boundary extending
from the center of the first North Pacific low, which will bring
some warmer air, precipitation, and wind from Kodiak Island
northward to the southern mainland. If this scenario materializes,
there is a potential that a barrier jet may develop along the
northern Gulf coast from Prince William Sound to the Copper River
Delta area. Uncertainty emerges in the track, position, and timing
of these systems. The GFS continues to be the wettest compared to
the other drier solutions. Out west, a broad trough will settle
just south of the Aleutians while weak, embedded shortwaves pivot
around the eastern periphery of the aforementioned trough. This
will bring a wintry mix of rain/snow and gusty winds along the
southern portion of the Aleutians and into the Bering Sea.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 411 Gale Warning 412 413 170 172 173 178
185 Heavy Freezing Spray Warning 411 412 414 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CQ
MARINE/LONG TERM...MK/MF