Storm Warning 184, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
413 AM AKST Sat Dec 28 2024

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

The primary hazard over the next few days will be strong
outflow/gap winds, with associated blowing snow and reduced
visibility in areas with transportable snow. A Winter Weather
Advisory remains in effect for Thompson Pass through Sunday
morning, as reports indicate over 8 inches of low-density snow
has fallen in recent days. Winds are currently gusting above 30
mph and are expected to increase later today into Sunday. Blowing
snow concerns should diminish once the snow is sufficiently
scoured out, though strong winds are likely to persist through at
least Monday.

In Whittier and Passage Canal, gusts exceed 30 mph, while Seward
is seeing gusts over 20 mph. Blowing snow is less of an issue in
these areas due to limited snowfall as of late.

For Anchorage and nearby regions, VIIRS Nighttime Microphysics
imagery shows stratus and/or fog across much of the Mat-Su
Valley, extending south into Anchorage, the Turnagain Arm, and
along the Seward Highway into the Kenai Peninsula. Observations
report fog or low ceilings beneath a 3-4 kft stratus deck. Light
northeast winds through the Mat Valley into Knik Arm appear to
have pushed the fog/low stratus deck southward. Until winds
increase and promote mixing, much of this area will likely
alternate between fog, stratus, and/or occasional clear skies
today.

Otherwise, generally quiet weather will persist through the
weekend into early next week. The Gulf of Alaska remains
unsettled, with a few weak areas of low pressure. A more notable
low-level trough is bringing light precipitation this morning from
Prince William Sound north through Valdez and into the Copper
River Basin. Forcing is limited, with some enhancement from a
passing shortwave trough to the north, so snowfall accumulation
is expected to be minimal. Farther south, Cordova airport has
reported snow and rain in recent hours, while the nearby SNOTEL at
Mt. Eyak shows a 3-inch increase in snow depth overnight
coincident with temps hovering near the freezing mark.
Precipitation in all these areas will taper off today as the low
to the south weakens, supported by the HREF showing less than a
10% probability of 1 inch of snow in any populated areas.

Upper-level ridging will amplify across southcentral Alaska this
weekend as the upper-level trough exits. Surface high pressure
will builds into early next week and become centered over Yukon. A
strong pressure gradient will sustain gap winds through Valdez and
the Copper River Delta. Temperatures will remain near or slightly
below climatological norms for most of southcentral Alaska, with
the coldest air since November.

Looking ahead to Monday, confidence is high that southerly flow
and a potential front will enter the area, starting near Kodiak
Island. Light snowfall may also develop on the Gulf side of the
Kenai Peninsula, though model spread remains far too large for
details. Most significant weather appears likely to remain west of
the region, with a generally dry pattern set to prevail across
southcentral Alaska.

-Brown

&&

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

The bulk of the weather will be along the Aleutian Chain working
eastward through Sunday as a front stretches across the Bering and
Aleutians. The attached parent low in the western Bering Sea
nudges northwards and ends up between Attu Island and Kamchatka
Peninsula through today. A second low develops near the base of
the front south of the Eastern Aleutians today and rapidly
strengthens by Sunday morning. The has been some model inconsistency
over the last several days but consensus is showing better
consolidation of the low tracking over the Eastern Aleutians,
placing the stronger winds along the southern Alaska Peninsula.
Areas of storm force winds and higher gusts are likely through
Cold Bay, King Cove, and False Pass, with high end gales
elsewhere. Unalaska will stay mostly out of the area of strongest
winds, but is expected to see a period of gales. The
aforementioned low will spend Sunday and Monday traveling north
across the eastern/central Bering, reaching the Pribilofs by late
Sunday night. Along the Southwest coast, from Pilot Point to
Kipnuk, winds will reach high end small craft to low end gale
force. Stronger winds reaching storm force will remain just
offshore in the eastern Bering and higher gusts are likely
through the gaps and passes north of the Alaska Peninsula.

&&

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

There will be some adjustments to the broad upper level trough
extending from the Russian Far East across the Aleutians and
Bering into the Gulf of Alaska through the forecast period. The
jetstream support for the main storm track sags into the Western
and Central North Pacific and Western Bering. The Eastern portions
remain more or less in place and weaken into a broad trough
through Friday. A number of low centers transit through the
pattern. An upper level ridge builds from the Western Canadian
Provinces across most of Mainland Alaska into the Russian Arctic
Coast. This ridge will help spread drier and cooler weather over
much of the Interior and Southern Alaska.

A series of lows and fronts work their way across the Aleutians
and Bering through the week. Locally moderate precipitation
starting as snow, but changing to rain will spread over the
Aleutians and Bering and into Southwest Alaska and the Alaska
Peninsula. Occasional periods of gusty surface winds will
accompany the fronts. A developing low over the North Pacific
Thursday brings periods of gale force winds into the Western
Aleutians Thursday morning, diminishing Friday morning while
extending the gusty wind field over the Aleutians to the AKPEN. In
the East, a low center meanders around the Gulf with areas of
rain across Kodiak Island, Prince William Sound and the rest of
the Southcentral coasts. Areas of more isolated to scattered snow
are expected further inland. Widespread Easterly gusty winds with
patches of gale force gusts near Kodiak Island occur Tuesday
through Wednesday night, diminishing.

&&

.AVIATION...

PANC...A combination of low stratus and freezing fog currently (as
of 4am) sits below 3-4kft ceiling across much of the Anchorage
area. Webcams and nearby observations suggest a light northerly
wind across the Knik Arm has pushed these IFR/LIFR ceilings close
to the Anchorage Airport. Included a tempo group in the 12z TAF to
account for this, though confidence is admittedly low.

Conditions should improve by later this afternoon as light
northeast winds should mix out and dry the lower atmosphere. Once
that occurs, VFR conditions with no ceilings and a light northeast
wind are to prevail into Sunday.

-Brown

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
257 PM AKST Sat Dec 28 2024

AKZ102-290400-
Anchorage-
Including the cities of Anchorage, Eagle River, Indian,
and Eklutna
257 PM AKST Sat Dec 28 2024

...PATCHES OF DENSE FOG LINGERING THIS AFTERNOON ACROSS THE
ANCHORAGE BOWL AND EAGLE RIVER...

Areas of dense fog will linger across portions of the Anchorage
Bowl north to near the Knik River Bridge. The fog is thickest
from Ted Stevens Airport north to the Knik River Bridge and
generally west of the Glenn Highway along the Knik Arm. Any areas
of locally dense fog are expected to persist through this evening
and possibly into the overnight hours.

Expect poor driving conditions in areas of low visibility. If
driving, be prepared for rapidly changing visibility and slick
spots developing on roadways. Slow down, use your headlights, and
leave plenty of distance ahead of you.