Gale Warning 986, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
858 PM AKST Mon Dec 30 2024

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

Currently, quiet weather is prevalent over much of Southcentral
due to the influence of upper level ridging that is centered
between the Yukon and Eastern Alaska. The Copper River Basin,
however, is experiencing dense fog due to a deep temperature
inversion and low level saturation. This fog has persisted all day
and will likely continue into Thursday as there is not enough
upper level forcing to dissipate it. Visibility could drop to
less than one mile in areas of dense fog. A couple of weak upper
level shortwaves ahead of a low to the south of Kodiak are
passing through the Kenai Peninsula, Anchorage Bowl, and Mat- Su
Valley and are preventing fog formation in those areas. The
aforementioned weak shortwaves are allowing generating
precipitation along Western Prince William Sound and the Kenai
Mountains. Whittier is receiving a mix of rain and snow. Some of
this precipitation is spilling over into Portage Valley, allowing
for snowfall. The inland areas as well as Eastern Prince William
Sound are expected to remain dry.

Now to address the previously advertised low south of Kodiak. It
is continuing to approach Kodiak Island from the south and is
already impacting the Island with gusty winds and rainfall. The
low will take a westerly turn once it arrives just south of Kodiak
Island Tuesday morning due to the influence of the previously
discussed high pressure in-between the Yukon and Eastern Alaska.
Again on Tuesday morning, high-end gale force winds will impact
the waters around Kodiak Island including Kamishak Bay, the
Barren Islands, and even around Augustine Island. Shelikof Strait
will experience storm force winds until Tuesday night due to a
favorable orientation of winds (north-easterly). Rainfall will
become quite heavy in Kodiak City itself as winds take on a more
northeasterly direction.

As the low exits to the West, winds will begin to lower in
strength and precipitation will lighten. Behind the low will be a
weak inverted trough for Wednesday. Compared to yesterday,
guidance has it staying away from the northern Gulf and tracks it
through Kodiak Island, allowing precipitation and gusty winds
through the western gaps to linger until Thursday afternoon. As a
result of this more southerly track, most of Southcentral will
remain dry with the exception of the exception of parts of western
Prince William sound. Uncertainty arises for Thursday
synoptically with the high being depressed by an Arctic trough. It
is uncertain what changes this might bring and what track the
trough will take, but one thing that is likely is that
Southcentral will continue to be dry with seasonal temperatures.

-JAR

&&

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

A low exits into eastern Russia while its front lingers along the
western coast of Alaska. Gusty winds and added moisture along the
front will continue bringing snow showers and the potential for
blowing snow to the western Capes, the Kuskokwim coast, and
Nunivak Island through tonight. On Tuesday, the front will weaken
and drift slightly westward towards the Pribilof Islands by
Tuesday night, bringing with it snow showers and elevated winds.

Most of Southwest Alaska will remain under high pressure through
the forecast period and, thus, can expect cooler temperatures and
clearing skies. Showers will linger for the Alaska Peninsula and
eastern Aleutians through Thursday as a result of a low traversing
the North Pacific close to the Aleutians.

Across the rest of the Aleutian Chain and the Bering Sea,
conditions will be a bit more unsettled yet benign in the way of
impacts. Showers will decrease tonight through Tuesday across the
central Bering and Aleutians as a narrow ridge builds. The
aforementioned North Pacific low and its front will provide
showers for the central Bering/Aleutians on Wednesday before it
weakens on Thursday. Broad troughing with embedded weak
disturbances near the western Aleutians will maintain
precipitation and light cyclonic flow as winds gradually shift
south and then east tonight through midweek. Winds may be
variable at times across the western and central Aleutians and
these weak disturbances interact with a pressing ridge from the
east.

A stronger North Pacific low is expected to reach the western
Aleutians around Thursday morning. Its front will lift parallel to
the Islands though its progression could be stunted by the
projected high pressure over the northern half of the Bering Sea.

Fenrich/rux

&&

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

An upper level high that had tracked across the Alaskan Mainland
moves off into the Arctic as a weak trough slides Southward across
the Yukon Territory Friday. An upper level trough extending from
the Bering low slides along the Western Alaskan Coast helped to
complete the break through the weekend. The source area ridge
stretching from Southeast Alaska will become re-established across
the Alaskan Interior by Sunday. Cooler and drier conditions will
not change much in the transition through the forecast period. An
ECMWF/GFS blend handles forecast strengths and tracks into the new
week with little problem. Across the Southern areas, an elongated
trough from Eastern Asia across the Bering into the Gulf of
Alaska carries the active weather. An upper level low center
meanders around the Western and Central Aleutians, providing the
support for surface lows, fronts and troughs all the way across to
Southcentral Alaska.

Some lingering areas of rain or rain-snow mixed across Kodiak
Island and The Alaska Peninsula give way to the first low and
front moving over the Aleutians on Friday. Gusty winds with areas
of gale force gusts extend from the North Pacific into the Bering
ahead of the front. Heavier rains and winds approaching gale force
moves over Kodiak Island Saturday and will spread over the
Eastern Kenai and Prince William Sound Sunday. Some locations will
see heavy rain over Kodiak Island up to Prince William Sound as
the surface low center moves in. A second well developed North
Pacific low continues the heavy rains from the Eastern Aleutians
and AKPEN, and spreads them to the Canadian border, with gusty
winds across the Gulf of Alaska through Monday. Inland locations
from the Shumagin Islands to the border will see snow.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist. Expect
northerly wind from Knik Arm to continue through the period.
Higher mid-level clouds will begin to come overhead late Tuesday
night.

MTL

&&