Gale Warning 292, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 AM AKDT Sun Mar 17 2024

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

The forecast remains on track as the first of two lows and
attendant shortwave troughs lifts to eastern Prince William Sound
this morning. A deformation band with a mid-level trough extends
to the northwest of the parent low, with widespread light snow
from Cook Inlet north to Talkeetna. This band will likely have an
eastern edge right over Anchorage this morning before moving back
to the west today as the second low moves north and the upper-
level wave becomes a bit more negatively tilted. Snow
accumulations will generally be light, with around an inch or less
from Kenai to Talkeetna and around 1 to 3 inches west toward
Skwentna.

This second low then moves from south of Seward to the entrance of
Prince William Sound Sunday night through Monday morning. The
associated shortwave lifts slowly from the Kenai Peninsula to the
Copper River Basin through Monday, shifting the southeasterly flow
southerly and southwesterly from west to east Monday. The result
will be the aforementioned deformation band moving slowly east
across the Western Kenai Peninsula into the Mat-Su Valleys by
Monday morning. Light snow is expected to increase in intensity as
it moves east, with a quick burst of 2 to 4 inches of snow
possible from Anchorage to Palmer and Talkeetna.

Similar amounts of snow are expected late Sunday into Monday for
eastern Kenai Peninsula and Prince William Sound communities, as
well. The exception will be Cordova, where temperatures  will
remain warm enough for mostly rain until the system exits the
region.

A ridge of high pressure then builds from the western Gulf to the
northern Gulf late Monday through Wednesday with quiet weather
through midweek.

-TM

&&

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

Quiet conditions continue today for most areas. Winds coming off
the sea ice are still producing areas of freezing spray across
portions of the Bering Sea and heavy freezing spray today for
areas along the ice edge in the northern Bering. Snow showers
across the central Bering and the eastern Aleutians/southern
Alaska Peninsula will likely continue today until the pattern
shifts tonight. A low pressure system moves out of the North
Pacific and towards the Aleutians tonight and will bring active
weather back to the Aleutians, southern AKPen, Pribilofs, and
portions of Southwest Alaska. After multiple weeks of northerly
flow in the eastern half of the Bering Sea along with a
significant southward advance of the sea ice, southerly flow will
bring a much warmer regime and both push sea ice back northward
and begin to break up and melt ice along the southern edge. This
will allow for a transition from snow to rain for many areas
following the front, as well as a warming trend for Southwest
Alaska. The transition from snow to rain will be relatively quick
for the eastern Aleutians and southern Alaska Peninsula, with
only a quick shot of snow in the early morning. As the front
progresses northwards towards the Kuskokwim Delta coast,
temperatures are slower to rise. Due to this, precipitation and
winds are likely to result in blowing snow concerns, or possibly
blizzard conditions, Monday night into Tuesday morning. There may
also be a period of blowing snow concerns across the Pribilof
Islands ahead of the warmer air Monday, however, there still
remains some uncertainty.

&&

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

The long term forecast remains largely unchanged. The upper level
pattern will be highly amplified, featuring deep troughing over
the Bering Sea and Aleutians and a stout ridge across much of
Mainland Alaska and the Gulf. This large scale weather pattern
will favor warmer than average temperatures across Southern
Alaska. While drier weather and lighter winds are expected for
Southcentral Alaska under the ridge, much more active weather will
be in store for the Bering Sea, Aleutian Islands, and Southwest
Alaska as several storms move through. The biggest challenge in
the long term will be honing in on the track and evolution of
these storms, which will then inform where the strongest winds
(likely to gale force or higher) and heaviest precipitation are
expected. Forecast uncertainty increases by Friday among the
operational global models. There are hints that an incoming
shortwave will be strong enough to impact the ridge, but models
diverge on whether the weakened ridge will remain over
Southcentral, or if it will be displaced into Canada.

- KC

&&

.AVIATION...

PANC...MVFR to IFR ceilings Sunday morning are expected to
continue through Monday afternoon. Periods of light snow will peak
Early Monday morning with a total snow accumulation of 2 to 3
inches. Expect VFR ceilings and drier conditions Monday afternoon
through the remainder of the week.

-ER

&&