Gale Warning 125, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
542 AM AKST Tue Feb 7 2023

.ANALYSIS AND UPPER LEVELS...

A broad trough of low pressure extends across the eastern Bering
Sea into the Gulf of Alaska. A few weak upper level waves within
the trough is moving north from the Gulf into Southcentral. This
is leading intermittent snow showers mainly along Prince William
Sound, the southern Kenai Peninsula and into Cook Inlet. Some
light snow showers are also being reported over Bristol Bay and on
the western side of of the mountain ranges. Out west, a few
transient lows continue to move through the Bering Sea and
Aleutian Chain, with a North Pacific low approaching near Kiska.

&&

.MODEL DISCUSSION...

Model guidance continues to remain in good agreement with respect
to the placement and intensity of synoptic scale features at the
surface and in the upper levels. Weak upper- level waves will
continue to move north from the Gulf into Southcentral midweek.
The main challenge is the timing of these waves and snowfall
amounts along the southern half of the region.

&&

.AVIATION...
PANC...VFR conditions with light winds will persist through
midday. Snow returns around 08th/03z with ceiling/visibility
between MVFR to IFR.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3;
Tuesday through Thursday night)...

Multiple shortwaves and attendant surface troughs continue to
rotate around a broad upper-level trough axis stretching from the
Bering Strait to Kodiak Island. The first of these is associated
with a compact surface low east of Middleton Island lifting north
toward Kayak Island this morning. This low, and upper-level wave,
are producing widespread showers that are moving over the eastern
half of Prince William Sound and the Copper River Delta.
Instability from the wave and cold air aloft have resulted in some
intense shower activity for these locations, with bands of
moderate to heavy snow showers persisting for the coastal
mountains, as well as Cordova, Valdez and Thompson Pass. These
showers will continue into early Tuesday afternoon before the low
and attendant wave move northeast with several additional inches
of snow possible for the aforementioned locations.

Farther west, a second wave and surface trough will northeast from
the Alaska Peninsula to the Kenai Peninsula today, and eventually
into Prince William Sound for Wednesday morning. The negative
tilt of the upper-level shortwave and weak moisture advection
should help to support widespread light snow from Homer north
across the Anchorage Bowl this afternoon and into the Mat-Su
Valleys later this evening. There is still some uncertainty as to
the extent and intensity of the snow, as some models are
suggesting a weakening of the trough in favor of the development
of a surface low over the northern Gulf. If the best dynamics
slide east of Cook Inlet, this would likely diminish the areal
coverage of snow later today from Kenai on north.

By tonight, however, yet another shortwave will move from the
AKPen toward the Kenai Peninsula. The negative tilt of this trough
and developing southeasterly flow will likely help guide the
aforementioned surface feature, whether trough or deeper low, into
western Prince William Sound, before stalling and weakening.
Again, the upper-level flow should draw moisture westward across
the Anchorage Bowl and north to the Mat-Su Valleys for Wednesday
morning. The trough is then expected to linger over the area
before lifting north late Wednesday evening. A general 1 to 3
inches of snow is possible across these locations, with locally
higher amounts possible in favored upslope areas, such as the
Anchorage Hillside and areas from Palmer north and east.

This pattern will also favor the continuation of snow showers
across the coastal mountains through early Thursday before a
surface ridge builds from the west and flow aloft switches from
southerly to northerly, allowing colder and drier air to move in
over Southcentral.

&&

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

Weather conditions across Southwest Alaska are expected to be
relatively mild over the next few days. Cold air advection will
continue to filter over the Mainland, with sub-zero temperatures
expected nearly everywhere (save for the southern Alaska
Peninsula) tonight and Wednesday night. Daytime temperatures will
increase marginally, into the single digits. Lingering light
snowfall has been observed throughout the night, but should taper
off through this morning.

&&

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

Broad troughing embedded with a few weak surface lows exists
across the Bering Sea and Aleutians. Overall, relatively quiet
weather will persist. Periods of snow showers will linger across
the Chain, as well as brief periods of localized small craft
winds. Cold air advection along the eastern Bering Sea will
continue to produce areas of heavy freezing spray along the ice
edge through tonight.

&&

.LONG TERM FORECAST (Friday through Monday)...

Low pressure is progged to move from the western Pacific, deepen
and lift through the central Aleutians by mid week. By Friday,
this low will deepen to 960, or lower, as it crosses the Aleutian
Chain, somewhere in the vicinity of Adak through Cold Bay. Model
guidance is still honing in on the details, but the big picture is
there. This low will slowly move towards Bristol Bay through the
weekend. Current trends are not bringing this low much inland (or
at all), thus a large influx of warm air is not anticipated.
Precipitation will spread from west to east, ending a short
reprieve from dry in Prince William Sound. Trends are showing that
the Anchorage Bowl will see limited precipitation as Turnagain
Arm Winds look to ramp up again late next weekend. Upper level
troughing will exist from Norton Bay, south through the Panhandle
and it's attendant surface low will still be impacting the eastern
gulf to panhandle as the workweek opens up.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Heavy Freezing Spray: 160, 180, 185, 414
		 Gale Warning: 130.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MF
SOUTHCENTRAL ALASKA...TM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...SS