Gale Warning 81, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
831 PM AKST Wed Jan 19 2022

.ANALYSIS AND UPPER LEVELS...

A complex upper-level pattern dominates the region as a broad
longwave trough extends across the Bering and Aleutians and into
Alaska. Downstream, an upper-level ridge stretches up from the
Northeast Pacific across Southeast Alaska and into Yukon
Territory. A low pressure system over the Gulf is moving north
while an upper level shortwave moving out of Southwest Alaska.
These two features are interacting and producing rain and snow
across Southcentral. Snow has been reported from Homer northward
across the Kenai Peninsula and into Anchorage and the MAT and
southern Susitna valleys. Across coastal locations a mix of rain
and snow have been observed. Otherwise a weak MAT valley wind has
developed with gusts up to 25 mph and a northerly down inlet wind
from Anchorage and down Cook Inlet. Gales have been observed
across the northern Gulf due to the formation of the barrier jet
on the north side of the low pressure system.

Southwest Alaska is seeing some light snow across the Kuskokwim
Delta associated with an upper level low spinning near the Bering
Strait. Otherwise areas of fog and stratus are occurring across
Bristol Bay, the AKPen and Eastern Aleutians. A frontal system
extends across the Western and Central Aleutians associated with
a North Pacific low well to the south of the Western Aleutians.
This is producing gale force winds to the north of the front
across the western Bering.

&&

.MODEL DISCUSSION...

Models are coming into better agreement with the developing
complex low and triple point low that forms along the front south
of the AKPen on Friday. There are still some slight differences
in the placement of these lows, which will influence the timing of
snow changing to rain across Southwest Alaska. Otherwise the
overall pattern looks good with a warming trend across
Southcentral and Southwest Friday into Saturday. The biggest
challenge will be timing the change over from snow to rain and if
or when any freezing precipitation may occur for both Southwest
and Southcentral for Friday into Saturday.

&&

.AVIATION...

PANC...Expect IFR visibilities due to snow with MVFR cigs through
the afternoon until snow begins to taper off, and conditions
steadily improve to VFR this evening. With the initial cloud deck
clearing out, low stratus or fog will have the potential to
develop over Cook Inlet and affect the terminal Wednesday night
into Thursday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3/Tonight through Saturday)...

Light snow has persisted across much of Southcentral today with
exceptions including the Susitna Valley and Kodiak Island. A
shortwave trough and associated surface low continue to promote
light snow showers from the Anchorage Bowl into Prince William
Sound. Accumulations ranging from 2 to 4 inches this afternoon
with the higher amounts confined to the Hillside. Eventually,
snow will taper off from west to east from the Kenai Peninsula and
Anchorage Bowl through the evening hours into tonight as both the
shortwave and surface low gradually depart the region. However,
snow is expected to persist into the overnight hours across the
Copper River Basin and locations could receive anywhere from 4 to
8 inches of total snowfall through Thursday morning.

The main story continues to be the expected warm-up by the end of
the week into the weekend as a series of shortwave disturbances
amplify a ridge of high pressure over the eastern Gulf and bring a
warm front northward into Southcentral. Accompanying this warm-
up will also be the addition of a tricky forecast in regard to
precipitation types, as the warm front brings an initial round of
snow before transitioning to all rain. Latest guidance has trended
the front and arrival of precipitation a hair slower though
timing of overall impacts should be similar to previous forecasts.
The front should reach Kodiak Island by midday on Thursday with
increasing snow before reaching the Gulf Coast tomorrow night.

Some areas may be slower to warm, resulting in potentially
heavier snow for locations such as Valdez through Friday and the
mountains of Prince William Sound Thursday night. Little has
changed in the overall forecast but the potential will exist for a
brief period of freezing rain across the Kenai Peninsula and
portions of the Valley, specifically north of Willow into Wasilla
midday on Friday. The threat for freezing rain is then forecast to
shift northwestward into the Susitna Valley through the evening
hours on Friday. Otherwise, continued warming will result in the
eventual transition of snow to rain for the remainder of
Southcentral with potential high temperatures over the weekend
still expected to approach 40 degrees Fahrenheit. Confidence in
placement of potential freezing rain remains below average as the
interaction of small scale features could potentially alter the
temperature profile of the atmosphere. Stay tuned to the forecast
as we will continue to highlight the areas of interest as the
details become more fine tuned.

&&

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

A shift in the weather pattern will get underway for the rest of
the week as southerly flow sets up over the Gulf of Alaska. By
Thursday, a North Pacific low and its associated front will bring
a chance of rain/snow mix for the AKPEN and snow across the
coastal areas and interior valleys. For Bristol Bay north and
west of Dillingham, blowing snow will be concern that will reduce
visibility to a half mile at times. Please see our Winter Weather
Advisory for more details. As the system departs to the east,
another North Pacific low and its front will follow on its heels
on Friday morning, bringing a greater chance of precipitation
through Saturday. The main challenge with both of these systems
will be the timing of the warm air advection from Bristol Bay
northward and how quickly the precipitation type will change from
snow to light freezing and then all rain. Stay tuned as we refine
the forecast for this week.

&&

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

A rather stagnant weather pattern will continue this week as a
pair of North Pacific lows and their associated fronts crosses
north of the Aleutians and into the Bering Sea. With these
systems, persistent east- northeast gale force winds, elevated
seas, and precipitation are expected to last through the weekend.
Winds will decrease to small crafts with a pocket of high end
gales for the Central and Eastern Aleutians through Friday night.
Additionally, a cold, Arctic airmass will move southward and help
transition the precipitation type to all snow showers for the
western Bering/Aleutians, while rain will be predominant in the
Eastern Aleutians.

&&

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

Gulf of Alaska...A front along the North Gulf Coast dissipates
Sunday. A new front moves to the Northern Gulf by Monday. Forecast
confidence is mixed with the timing and strength of the second
front. Gusty winds over the Gulf diminish late Saturday. Seas to
17 feet subsiding. Gusty winds ahead of the second front increase
to widespread gales across the Western Gulf and Alaska Peninsula
Sunday and Monday. Seas building to 20 feet over the Western Gulf
for Monday.

Aleutians / Bering...A well developed Central Bering low moves
through the Bering Strait by late Sunday. Weak low pressure forms
over the Western Bering Sunday. Gusty winds over the Central
Bering, diminish Sunday. Seas to 12 feet, subsiding. A North
Pacific low moves across the Eastern Aleutians Sunday, and into
Bristol Bay by Monday. Widespread gales over the Alaska Peninsula
and Bristol Bay for Sunday, diminishing Monday. Seas to 20 feet on
the Pacific side of the Alaska Peninsula Sunday and Monday,
subsiding.

&&

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

Model agreement is decent at best, but there are still quite a
few discrepancies in the long term. Guidance stays relatively
consistent for upper level ridging across the eastern Gulf,
extending northwards into the Mainland and tracking eastward
towards Canada. Longwave troughing dips down over the Aleutians, a
surface low developing at the base of the trough. This may create
a wet pattern across Southwest Alaska as well as along the
eastern Kenai and Kodiak Island as we enter early next week. It is
still too early to determine precipitation type at this point,
and will rely fairly heavily on how much warm air is able to make
its way over land. As it stands now, guidance is pointing towards
strong southerly flow for Southcentral, which may allow
temperatures to remain above freezing through early next week. The
back side of the trough will likely see a decrease in
temperatures as flow transitions to northerly, namely along the
Bering Sea and Western and Central Aleutians.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Watch: 141.
Winter Weather Advisory: 131, 161.
MARINE...Gale Warning: 119 120 130 131 138 139 155 165-179 351-414.
Heavy Freezing Spray Warning: 179 185 412 414.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MF
MARINE/LONG TERM...KZ/KM