Gale Warning 80, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
424 PM AKST Sun Jan 19 2025

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

Active weather continues across Southcentral Alaska as a robust
frontal system and associated low-pressure system over the
northern Gulf brings significant precipitation and wind to the
region. This system encountered an amplified ridge that shifted
into Canada, enabling dynamic lift and upslope flow along the
coastal mountains. Heavy snow impacted Turnagain Pass and Thompson
Pass, where Winter Weather Advisories remain in effect. These
conditions align with ongoing Winter Weather Advisories for
Turnagain Pass (until midnight), Thompson Pass (until 9 AM
Monday), and the Copper River Basin (until 6 AM Monday).

Elsewhere, precipitation types varied widely, with mostly rain
interspersed with some snow across the western Kenai Peninsula.
Valdez experienced heavy snow early in the day, transitioning to
rain as low-level warming took over, while Glennallen briefly
reported freezing rain before switching to plain rain. Whittier
received decent snowfall, but nearby Portage saw little to none.
For Anchorage and the Mat Valley, while light mixed precipitation
has already been observed, the best chance for snowfall will be
this afternoon into the evening with the passage of the upper-
level trough and the associated deformation band on the backside
of the surface low. Brief minor snowfall accumulations are
possible with temperatures hovering near or even above freezing.

The current system will wind down tonight as the trough lifts
northeast into the Copper Basin, clearing precipitation from west
to east by Monday morning. An transient upper ridge will
temporarily build behind the exiting system, providing a brief
reprieve with calmer winds and drier conditions on Monday.
However, this lull will be short-lived as another shortwave trough
and frontal system enter the Gulf by Tuesday morning.

While there are differences in the synoptics, the progression and
impacts of this next system will closely mirror the recent
pattern, with strong southeasterly flow driving precipitation into
coastal terrain. Snow will redevelop across the Kenai Mountains
Tuesday afternoon, intensifying and spreading into the central and
eastern Chugach Range by Tuesday night. Precipitation and wind
impacts will persist into midweek, continuing the active weather
pattern across the region. Timing for this next system remains
consistent with earlier forecasts, though the GFS continues to
suggest a slower progression compared to other model guidance.

Eovino

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Sunday morning to Wednesday morning)...

Currently, a trough is passing through the southwest mainland,
which is allowing for widespread light showers to form. A warm air
mass in place from southerly flow means that these showers are
mostly in the form of rain except for higher elevations.
Temperatures aloft remain below freezing so no freezing rain or
sleet is expected in the short term. These showers are expected to
linger until Monday night when a ridge builds in and pushes the
moisture out of the region. The Aleutians are seeing rain and gale
force winds as a North Pacific low slowly tracks eastward. The
Pribilof Islands are currently under a Winter Weather Advisory for
blowing snow until Tuesday morning. This is due to the gale force
winds as well as cold air wrapping around the low which, combined
with the moisture and lift the low is delivering to the area,
could bring about snow and blowing snow.

As the low approaches the mainland on Tuesday, it will weaken and
the precipitation band will become less organized. Also, the
winds diminish as the low dissipates into a shortwave trough.
Showery precipitation will affect the mainland once again as
moisture moves in. Southerly flow will remain in the mainland,
which means that the warm air mass from before will still be in
place. This means that most precipitation will be in the form of
rain except for the northernmost areas of the domain and higher
elevations. As the main core of the former low passes through the
Southwest by Wednesday morning, cold air that has wrapped around
the back of the system will move in from the south, dropping
temperatures below freezing north of Dillingham by Wednesday
afternoon. Lingering moisture means that some snow showers could
form north of Dillingham through Wednesday afternoon.

Meanwhile in the Bering, after a short period of ridging, another
low will approach from the west, pushing into the western
Aleutians by early Wednesday morning. Winds and precipitation
chances will increase in response to this low, with the winds
reaching high-end gale force strength. This low will pass through
a colder air mass, so snowfall ahead of the core of the low may be
possible depending on the vertical profile of temperatures. By
Wednesday afternoon, a compact low will swing up from the south,
pushing the previous low northwards and bringing a burst of warm
air, potentially storm force winds, and precipitation to the
central Aleutians. The exact scenario that will take place on
Wednesday is still uncertain and is subject to change.

-JAR

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

Active weather will continue along the south central coast of
Alaska ahead of a large area of low pressure expected to move into
the state from the west around midweek. This low will transit
southwest and south central Alaska by Friday and Saturday and
bring much colder temperatures to most of the state for the
weekend. By Sunday, high pressure will bring drier conditions
gradually building east into the AKPEN and western Kenai by late
Sunday.

&&

AVIATION...

PANC...

Light northerly winds of 5 to 10 kts this afternoon are expected
to shift to south-southeasterly tonight. Periods of light snow
and/or a rain-snow mix will continue will become more steady this
evening as the precipitation band shifts north and east. VFR vis
and ceilings may drop to IFR at times as the band moves through.
Conditions will improve after 09-12Z with some lingering light
precipitation through mid-morning Monday.

&&