Gale Warning 381, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
406 PM AKDT Fri Apr 12 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
This afternoon through Monday)...

Aside from some updates to the precipitation forecast, only minor
changes have been made since the previous forecast package. Our
current spell of more active weather will subside through tomorrow,
ushering in quieter weather for most of the weekend. No major
hazards are expected through Monday.

Diving into the details...a weak surface low currently lingers
near Prince William Sound, while an upper level longwave trough
approaches from the west. The surface low's decaying front
continues to produce precipitation across Prince William Sound.
Areas like Whittier and Cordova have transitioned from snow to
rain as temperatures climb into the mid-30s, though Valdez
continues to hold onto snow.

Further west, lift associated with the incoming upper level
trough is producing snow showers along west-facing slopes of
Talkeetnas, Chugach Front Range, and Kenai Peninsula mountains.
Parts of Anchorage also saw light snow earlier today as low level
convergence (from southeasterly flow up Turnagain Arm and
southwesterly flow up Cook Inlet) produced persistent
snowfall/graupel. However, with the longwave trough progressing
eastward through the afternoon and evening, precipitation in
these areas will taper off as the showers move into the Copper
River Basin.

As the longwave trough moves east, a weak low forms in the Gulf
Saturday morning and drifts southward, leading to gusty, offshore
winds through the weekend. An upper level ridge gradually builds
in by Saturday afternoon, allowing clouds to gradually clear out
from west to east. Expect fairly pleasant, mostly sunny and dry
conditions with seasonable highs in the mid 30s to low 40s and
lows in the teens to 20s through Monday.

-KC

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA, AND ALEUTIAN
ISLANDS (Days 1 through 3: Tonight through Monday)...

Scattered snow showers continue to taper off this afternoon and
evening for the Kuskokwim Delta. Snow shower activity will linger
through the night for interior Bristol Bay, the northern Alaska
Peninsula, and the Lower Kuskokwim Valley before tapering off
early Saturday morning. Cold and dry northerly flow will take
hold of the weather pattern for Tonight through most of Saturday
across Southwest Alaska. Temperatures tonight look to dip into the
single digits and teens for mainland Southwest while the AKPEN
sees 20s. Temperatures look to rebound for Saturday with the AKPEN
and mainland Southwest seeing upper 20s to lower 30s for highs. A
weak upper-level shortwave looks to drop into the Kuskokwim Delta
Saturday night into Sunday morning before ridging builds in
during the day Sunday. Any snow accumulations look to be light and
mainly confined to the Kuskokwim and Kilbuck Mountains. As the
ridge builds in Sunday, there could be the chance for some patchy
fog across portions of coastal Bristol Bay.

The next notable weather-maker looks to arrive Sunday morning as a
North Pacific low lifts to the western and central Aleutian Chain.
There is some uncertainty in the ultimate track of the low, but
trends today hedge toward the stronger solution of the GFS/NAM.
A corridor of sustained storm-force winds is possible Sunday for
areas of the western Aleutians, particularly for eastern portions,
as well as for the central Aleutians Sunday into Sunday night.
Expect rain/snow mix at the start with a changeover to rain Sunday
afternoon as warm air works in. The front, now gale-force, makes
it to the Pribilof Island late Sunday evening with precipitation
starting as snow and eventually changing over to rain/snow mix
by Monday afternoon. The front continues its journey eastward
to coastal Southwest by Monday afternoon and moves inland of the
Kuskokwim Delta and Western Capes region of northwestern Bristol
Bay through Monday evening. There could be enough cold air in
place as the front arrives to get a period of blowing snow across
portions of the Kuskokwim Delta Coast, Nunivak Island, and the
Western Capes. Stay tuned as details become clearer about the
evolution and track of this system.

&&

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

A pattern shift is on tap in the long term forecast period. Expect
the ridge to break down. A series of North Pacific Lows will push
into the Gulf and moisture from the Central Pacific Basin will
move towards Southcentral. However, model agreement regarding the
timing of these lows is still not exactly in sync but they are
locking on to the concept of a wetter and windier pattern for
Kodiak, the Barren Islands and other parts of Southcentral. Given
its origin and potential orientation of these moisture fetches,
this may also lead to another precipitation event for the Prince
William Sound communities. For Southwest Alaska, the temperatures
will be below seasonal norms this forecast period but beyond that
the vagaries of the models leave much to be desired. Out west
over the Bering and NW Pacific, the models are all over the place.
The run-to-run continuity for the NW Pacific and Bering has been
poor for the medium range for multiple runs of the global models.

&&

.AVIATION...

PANC...Generally improving conditions are expected through the
night and into Saturday as an upper level trough passes by and
high pressure is able to build in behind the trough. This will
diminish the gusty south to southeasterly winds by this evening
and then turn them northerly overnight. There may be some light
snow showers and reduced ceilings as vorticity-maxima on the back
side of the low track overhead between 12Z and 18Z, but the
northerly flow will generally begin to advect in drier air. If
there is any ceiling/vis reduction Saturday morning, it will be
brief and conditions will quickly improve through the morning
hours.

&&