High Wind Watch 4, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
527 AM AKST Sat Feb 3 2024

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

The coldest morning so far this week for many locations across
Southcentral as clear skies and calm winds allowed for strong
radiational cooling overnight. The Copper River Basin showed the
coldest temperatures with multiple sites plunging to 35 to 45 below
zero as of 3 AM and with several more hours of cooling...could see a
drop of up to several more degrees. Anchorage and Eagle River also
saw their coldest morning with temperatures mostly ranging from 15
to 30 below. A Wind Chill Advisory remains in effect for Thompson
Pass through noon today as temperatures of 15 to 20 below and winds
gusting to 30 mph are resulting in wind chills of 40 to 50 below.
Winds should start to relax some and temperatures gradually warming
by this afternoon as the surface high over eastern Alaska continues
to translate eastwards into the Yukon.

With this the last day of very cold temperatures for this cold
spell, attention now turns towards a system that will lift up across
the western Gulf today and tomorrow. The parent system is currently
seen on water vapor imagery lifting through the western Aleutians
this morning with associated front lifting across the Aleutian
Chain. The front will continue to lift up across the AKPen and
Kodiak Island today bringing another round of snow. The snow will
spread north through the day, working up the Cook Inlet and Kenai
Peninsula by this afternoon. A surface low will develop just off of
the northern end of Kodiak Island then move up along the eastern
Kenai coast. While models are in good agreement with development and
timing of this low, there are differences in track and speed of the
low as it moves north towards Prince William Sound. The NAM develops
this low closer the Barren Islands and tracks it faster and closer
to the Kenai coast then the the GFS which has tracks in much slower
and further out in the Gulf. Have trended the forecast somewhere in
the middle for now with the potential for fine tuning the forecast
as the track of the low becomes more apparent. Regardless, northerly
winds will increase across the western Kenai and Cook Inlet and with
a more light and fluffy snow, the potential remains high for areas
of reduced visibility due to the ease at which this snow will blow
around. As such, a Winter Weather Advisory remains in effect today
through Sunday for snow and blowing snow for the western Kenai and
Anchorage Bowl. Thompson Pass is another location that can expect to
see several inches of snow and blowing snow. Thus, a Winter Weather
Advisory also remains in effect for Thompson Pass starting Saturday
night.

With the newly formed surface low tracking north towards Prince
William Sound, the eastern Kenai and Prince William Sound will also
see snow spreading north through the day today. Snowfall will
increase by Sunday morning as the surface low approaches and then
begins to weaken.

Another system will quickly follow on the heels of the
aforementioned system, bringing another round of snow that will
spread north through the day Monday. Once again, the NAM keeps the
surface low tracking off the eastern coast of the Kenai while the
GFS develops a much deeper low but takes a more easterly track out
towards the central Gulf. With such apparent differences, have again
trended the forecast somewhere in the middle for now and the finer
forecast details can be nailed down as models come into better
agreement.

- PP

&&

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

Key Points:

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

* Blizzard Warnings are in effect from now through Sunday morning
  for Nunivak Island and the Kuskokwim Delta coast, as well as
  Bristol Bay north and west of Dillingham.

Discussion:

The primary weather maker for Southwest Alaska, the Bering Sea,
and the Aleutian Islands through today will be a low currently
near Adak and its front, which is draped across the Southwest
coastline and the Alaska Peninsula. The main story with this front
will be blizzard conditions and moderate to heavy snow for the
Kuskokwim Delta and Bristol Bay, for which Blizzard Warnings are
in effect. Aside from minor increases in snow amounts and wind
speeds, the forecast remains largely on track. The biggest
uncertainties for today will involve the timing of precipitation
in Southwest Alaska (as model still differ with the speed of this
front) and for precipitation type in the Bering Sea and Aleutian
Islands (where temperatures are currently hovering near freezing)
as showers move through in conjunction with the occluded low
center.

By Saturday night, the low will exit towards Kamchatka Peninsula
while its front begins to shear apart. Precipitation will
gradually taper off, with a brief lull in between storms. The next
storm, however, will be well on its way into the Aleutians by
Sunday morning. A strong North Pacific low moves into the Bering
Sea on Sunday and lingers through Monday. Sustained, storm force
winds (>= 50 kt) could impact the Central Aleutians for several
hours, while the front associated with this low will bring another
round of precipitation across the region. There remains
uncertainty with the low track, but confidence is high for
sustained gales (>= 35 kt) and moderate precipitation along the
front. We'll continue to hone in on the forecast as confidence
increases. Looking ahead to Tuesday, yet another North Pacific low
makes its way towards the Alaska Peninsula and Southwest Alaska.

- KC

&&
.LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)...

A broad upper level low center over the Bering weakens as it
becomes a broad trough extending across the Alaska Peninsula
through the forecast period. Several shortwaves of moderate
amplitude slip along its southern periphery, supporting surface
features and periods of active weather through Friday. Models are
losing their consistency with the medium to large scale features
with the transient events through the week. Dry Arctic air is
expected to remain over most of Interior Alaska with outflow into
the Bering, driving gusty, but diminishing Easterly winds across
the Northern Bering. Shortwaves pushing surface lows and fronts
along the Aleutians and AKPEN bring gusty winds, especially
through channeled terrain, and locally heavy precipitation on its
Eastward tracks. New rounds of gusty winds and snow move into
Southwest Alaska through midweek. The front splits over the
Northern AKPEN, with the Southern portions heading across the Gulf
through Thursday. A North Pacific low and its front approaches
the Eastern Aleutians Thursday, with the front extending into the
Gulf of Alaska through Friday. 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...

Periods of intermittent fog/low stratus may develop over the
terminal this morning. Snow is expected to begin this afternoon
and persist through Sunday morning. Ceiling and visibilities are
expected to be predominately IFR to MVFR.

&&