Storm Warning 186, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
546 AM AKST Mon Dec 2 2024

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

Southerly flow into Southcentral continues as an upper level low
continues westward into the southern Bering Sea through Tuesday.
Multiple shortwaves and lows embedded within the southerly flow
will continue the active weather pattern bringing more strong
winds and precipitation mainly along the coast. The warming trend
throughout Southcentral will continue through mid-week.

Light precipitation proceeds to fall this morning along the coast
of Prince William Sound and throughout areas of the Kenai
Peninsula but will taper off throughout the day from west to east.
The strongest of the winds across the northern Gulf, Cook Inlet,
and Shelikof strait will also continue to relax throughout the day
today ahead of the next system making its way northward through
the Gulf. Models are coming into much better agreement on the
progression of the next low moving north-northwestward through the
Gulf towards Kodiak Island through Tuesday night. Winds in the
northern Gulf will begin to pick up by Tuesday morning with a
barrier jet producing a large area of gale-force winds along the
northern Gulf coast as well as additional pockets of gale-force
winds returning to Cook Inlet and Shelikof Strait through Tuesday
night. Ahead of this system, very light upslope precipitation is
possible along the Southcentral coast during the day on Tuesday,
but will become steadier and heavy at times by Tuesday evening as
the low's front approaches the coast. Steady upslope
precipitation, in the form of rain at sea level, will continue
through at least Wednesday as reinforcing waves stream up from the
south. Typical downsloping areas should remain mostly dry
throughout the period, although the initial push of precipitation
Tuesday afternoon into Tuesday evening may bring light
precipitation to the western Kenai Peninsula and Anchorage before
the strongest downsloping begins. With warmer air moving in aloft
and surface temperatures remaining below freezing, there is a
chance for light freezing rain to fall across these areas.

&&

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

A large upper low centered near the Pribilof Islands is producing
a large area of snow showers across much of the Bering Sea and
Aleutian Islands this morning as cold air streams southward across
the region. A weakening front extends isolated shower activity
along the Southwest coast and into portions of the Alaska
Peninsula, though the rest of Southwest Alaska is absent of
precipitation and areas of clear skies in the Lower Kuskokwim
Valley have brought temperatures as low as -20 in Sleetmute. The
most significant concern in the short term is in the Pribilof
Islands, where a series of mesolows underneath the Bering upper
low will bring the potential for periods of heavy snowfall and
blowing snow. Easterly winds gusting up to 35 mph will lead to
reduced visibility of one mile or less along with blowing snow,
dropping as low as one quarter mile at times. The greatest
potential lasts through tonight, whereafter uncertainty in the
track of mesolows and an arriving front means that snowfall and
winds may abate somewhat or potentially continue through Tuesday
afternoon. Regardless, the Pribilof Islands can expect to see
several inches of snowfall (2 to 5 inches) and periods of blowing
snow through Tuesday. Along the western and central Aleutians, cold
air and associated snow showers pushing southward will lead to
snow accumulations up to two inches through Tuesday night.

Further east, warmer air begins to push up across the Alaska
Peninsula and into Bristol Bay, warming temperatures above
freezing for the eastern Aleutians and Alaska Peninsula, though
temperatures rise only into the 20s for much of Bristol Bay,
especially along the Ahklun Mountains, where cold air at the
surface could dam up. Stratus is already spreading into portions
of Greater Bristol Bay and the Western Alaska Range, signifying
the arrival of another round of moisture into Southwest Alaska. An
upper-level trough lifts across the region tonight, brining
increased chances for precipitation as it enhances instability
aloft. Accumulations are expected to be light as precipitation
will be spotty, but above freezing temperatures look to make their
way into Bristol Bay while cold northerly winds keep surface
temperatures below freezing, leading to potential for freezing
rain as early as this evening. There is some uncertainty, however,
in the strength of the warm air surge and there is some potential
for the column to stay below freezing with this first round of
precipitation, thus leading to only light snowfall.

Freezing rain potential continues with a second round Tuesday
into Wednesday as warm air continues to move in aloft and a
stronger front brings steadier precipitation to the area. Higher
chances of freezing rain with greater ice accumulations are
possible with this second round, especially for the corridor from
Dillingham north to Koliganek, though conditions look favorable
for at least a trace of ice for the entire Bristol Bay region,
from the Western Capes to Iliamna and the northern Alaska
Peninsula. Aleknagik, a favored spot for freezing rain, has the
best potential to stay coldest and this may lead to a more delayed
arrival of freezing rain. Confidence in precipitation type
decreases for the Kuskokwim Valley and Delta, but freezing rain
(along with precipitation in general) would not likely begin for
these areas until Wednesday morning.

For the rest of the Bering Sea/Aleutians, a moderating air mass
will begin to see rain mix in with light snow showers for the
central/western Aleutians by midweek. For the central/western
Aleutians, showers gradually decrease in coverage through
Wednesday night, while the eastern Aleutians and Pribilofs can
expect steadier precipitation as a front sets up overhead.

Quesada/Rux

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

A series of lows are forecast to rotate from the North Pacific
and across the Alaska Peninsula into the Bering Sea through the
end of the week. Despite some uncertainty in strength, timing and
placement of each low, long term model guidance is in general
agreement with persistent southerly flow developing from the
Pacific side of the Aleutians into the Gulf of Alaska as a broader
trough takes shape from the Aleutians into the Gulf Coast. What
this means for Alaska is a relatively warmer and wetter pattern
unfolding for the foreseeable future. Ensemble means support the
idea of a trough becoming established across the region, its axis
oriented along the Alaska Peninsula and through the Aleutians by
the following weekend. Southerly surface winds from south of the
Aleutians and across the Gulf will change little, while weak
easterly zonal flow prevails across the Bering. Temperatures will
support rain along the coast into Prince William Sound, though,
further inland, without the presence of any significant wind or
advecting air masses, temperatures should remain cool enough for
any precipitation to fall as snow.

&&

.AVIATION...

PANC...Chance for on and off light snow through early this
morning. Otherwise, VFR conditions and light winds will persist.

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
1142 AM AKST Mon Dec 2 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0431 PM     Non-Tstm Wnd Gst 7 NW Palmer             61.68N 149.24W
12/01/2024  M46 MPH          Matanuska-Susitna  AK   Public

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
1144 AM AKST Mon Dec 2 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0742 AM     Snow             5 E Valdez              61.11N 146.22W
12/02/2024  M0.1 Inch        Chugach            AK   Public

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
246 PM AKST Mon Dec 2 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0431 PM     Non-Tstm Wnd Gst 7 NW Palmer             61.68N 149.24W
12/01/2024  M46 MPH          Matanuska-Susitna  AK   Public

&&