Gale Warning 149, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
540 AM AKST Fri Feb 2 2024

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

Another very cold morning across Southcentral as Arctic airmass
remains entrenched over the region and clear skies have allowed for
strong radiational cooling. Little in the way of low stratus and fog
this morning with the exception of a few areas along the Knik Arm,
Cook Inlet, and Kachemak Bay. Temperatures this morning are ranging
from around 30 to 40 below in portions of the Mat-Su Valley and
Copper River Basin, and 10 to 25 below for Eagle River, the
Anchorage Bowl, and Kenai Peninsula. Even the coastal areas along
the eastern Kenai and Prince William Sound have fallen into the
single digits to lower teens as gap winds subsided some overnight.
With surface high pressure in place, winds will remain light for all
but the normal gap flow areas.

A front will lift across the AKPen and Kodiak Island today. A
surface low will develop just off the southern coast of Kodiak
Island before moving eastwards into the Gulf. This system will bring
a quick shot of snow to the island with higher amounts of up to
several inches for the southern half of the island. The northern
half will likely see only minor accumulations. The rest of
Southcentral will remain dry today, though another system looks to
bring another round of snowfall by this weekend.

A low will lift north across the Central Aleutians into the Bering
Sea tonight with the front pushing eastwards towards the AKPen and
western Gulf. Another round of snow will spread across Kodiak but
with warmer temperatures being dragged north with this
system...should see a transition to rain by Saturday night as
temperatures warm above freezing. Snow will continue to spread north
across the Kenai Peninsula and up the Cook Inlet Saturday. Models
are in good agreement with triple-point low developing near Kodiak
and the Barren Islands Saturday night with gale force southerly
winds developing down the Cook Inlet and along the eastern Kenai
coast. With vertical temperature profiles still looking quite cold
and saturation looking to occur over a decent depth within the
dendritic growth zone, snow will be on the light and fluffy side.
The greatest snowfall amounts should be confined to the southern end
of the Cook Inlet and western Kenai.

- PP

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Today through Monday)...

Key Points:

* A series of storms moves in through Monday, leading to active
  weather and a gradual warming trend.

* A Winter Storm Watch for blizzard conditions is currently in
  effect for Nunivak Island and the Kuskokwim Delta coast from
  late Friday night through early Sunday morning.

* We're monitoring the potential for moderate/heavy snow and
  significant visibility reductions due to blowing snow for
  Bristol Bay on Saturday.

Discussion:

With the jet stream/storm track extending northward towards the
Bering Sea and Southern Alaska through Monday, expect active
weather and a general warming trend as a series of warm and wet
storm systems move in from the North Pacific Ocean.

The first storm is a low currently in the Western Bering Sea with
its front extending across the Northern Bering and Southwest
Alaska coast. Gales and light rain/snow associated with this
front will gradually subside through today as the low exits
towards the Kamchatka Peninsula.

The storm to watch will be one currently moving towards the
Bering Sea from the North Pacific. This broad, upper level low
with multiple embedded shortwaves will spawn multiple surface lows
as it moves through the Bering Sea this weekend. The first
surface low is currently pushing its front into the Western
Aleutians. The plume of moisture associated with this front
features precipitable water values of 0.75 inches and greater. As
such, the front is expected to bring plenty of precipitation as it
sweeps across the Aleutian Islands and Southwest Alaska. Areas
along the Aleutian Chain may see precipitation amounts as high as
0.5 to 1 inch with this front. In particular, Unalaska could see
over half an inch of precipitation in a 6-hour span as the front
moves through.

For Southwest Alaska, the approach of the front on Saturday will
bring the potential for moderate/heavy snow and blowing snow. A
Winter Storm Watch for blizzard conditions is currently in effect
for Nunivak Island and the Kuskokwim Delta coast. While winds will
be on the lower end of what's ideal for blizzard conditions,
temperatures well below freezing should support lower density snow
that's easier to loft and transport. As such, significant
visibility reductions are possible even with relatively weaker
winds. While no watches, warnings, or advisories are currently in
effect for Bristol Bay, we're monitoring the potential for blowing
snow and 6+ inch storm total snow amounts on Saturday.

By Sunday morning, this second storm system follows the path of
the first and exits towards Kamchatka Peninsula. A third low then
moves towards the Central Aleutians from the North Pacific,
bringing the next round of active weather. By Monday, the
continued southerly flow and warm air advection associated with
these three storms will bring maximum temperatures into the teens
and 20s for Southwest Alaska and into the 30s for the Alaska
Peninsula, Aleutian Islands, and Bering Sea.

-KC

&&

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

A broad upper level low center is pushing its way across the
Bering towards the Eastern Aleutians through the forecast period.
Several shortwaves of moderate amplitude rotate along its southern
periphery, supporting surface features and periods of active
weather through Thursday. Models remain consistent with the medium
to large scale features, but lose their certainty with the
transient events through the week. Dry Arctic air continues its
spread over most of Interior Alaska with outflow into the Bering,
driving gusty Easterly winds approaching gale force across the
Northern Bering. Relatively warm, moist air rides over a North
Pacific ridge across Southern Alaska. Local areas of gale force
winds over the Western Aleutians diminish in areal size and
overall strength as each trough moves Eastward, then into the
Bering by Thursday. Precipitation starts as snow and changes to a
rain-snow mix and then all rain over the Eastern Aleutians, Alaska
Peninsula. Mixed precipitation moving into Southwest Alaska
through midweek. Looks like the front splits over the AKPEN late
Monday, sending rain into Kodiak Island and the Gulf of Alaska.
Gusty Northwesterly winds move across the Shumagin Island Monday,
and Southeasterly gap winds approaching gale force move over the
Barren Islands Monday into Tuesday. Rain and snow mixed or rain
will spread over the coastal portions and Prince William Sound
through the end of the forecast. Inland areas remain under periods
of snow.

Kutz

&&

.AVIATION...

PANC...

Areas of fog and low stratus may continue through this morning
and visibilities may drop to IFR at times.

&&