Storm Warning 163, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
604 AM AKST Mon Nov 4 2024

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

Key Points:

- The Winter Storm Watch for Turnagain Pass and Summit Lake has
  been upgraded to a Winter Storm Warning. Snowfall rates of 1 to
  3 inches per hour combined with strong easterly winds will
  likely create whiteout conditions through Turnagain Pass between
  6am and 1pm on Tuesday.

- The Blizzard Watch for Thompson Pass has been upgraded to a
  Blizzard Warning.

- High Wind Watches remain in effect for the Anchorage Hillside
  and Turnagain Arm, but are looking more likely.

The compact upper low and surface low over the Prince William
Sound that brought widespread light to moderate snow will quickly
depart to the east today, making way for a brief period of calm,
and even sunny weather. Colder air wrapping in behind this system,
in addition to clearing skies, will cool temperatures slightly
from what has been observed recently.

A well-modeled and strong low remains on track to move into the
eastern Bering later tonight, sending its front into Kodiak Island
overnight and into Southcentral tomorrow. Strong winds and
moderate to heavy rain will fist hit Kodiak overnight. Widespread
storm force winds are expected for the Gulf marine areas and
Barren Islands as the front moves north. Impacts will be felt
across Southcentral, but the Sound, Kenai Peninsula, and Turnagain
Arm will feel the brunt of it. Coastal communities of Seward,
Whittier, Valdez and Cordova will see mostly moderate rain from
this event, but heavy snow and wind are expected above 800 to 1200
feet with the front. With this, Winter Storm and Blizzard
Warnings are in effect for Turnagain Pass and Thompson Pass
respectively. Despite some warm air, dynamic cooling should keep
the precipitation type as snow through Turnagain Pass for the bulk
of the front, but some mixing with rain can't be ruled out as the
event progresses.

High winds are looking more likely for Anchorage and Portage, but
some differences in lee-side troughing need to be investigated
further. With the low far to our south, a down-Inlet gradient is
favored for the majority of the event. However, some guidance is
developing a ridge-line inversion near the timing of peak winds
and frontal passage through the Sound. If this develops, some
lower elevation winds are possible, and winds along the Hillside
are likely. Even with the strong gradient, areas like Upper Potter
Valley and Upper Bear Valley are likely to receive strong gusts
whether or not an inversion sets up. Stay tuned.

Precipitation type along Cook Inlet should be mostly rain, with
most of the precipitation falling from Ninilchik South. Some
colder air aloft is trying to hold on, but the strong down inlet
flow and downsloping will likely warm conditions quickly.
Anchorage may hold on to cold enough air for a brief half inch of
snow before transitioning to rain. For the most part though,
precipitation from Kenai City north into the southern Mat-Su
should be mostly downsloped.

After the front passes through Tuesday afternoon, expect
widespread temperatures in the upper 30s to low 40s. South to
southeasterly winds will keep temperatures above normal through at
least Thursday when an additional low moves into the southern
Gulf and changes the wind direction back to northerly. This may
help to cool things back down, but temperatures are likely to
remain above average due to cloudcover.

&&

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

A storm force low is still on track to cross over the Eastern
Aleutians today and track northward towards Cape Newenham by
Tuesday morning. Storm force winds will reach the Eastern
Aleutians and southern Alaska Peninsula first, this morning,
followed quickly by the Pribilof Islands and Bristol Bay coast
this afternoon. Strong winds are also expected to filter across
interior Bristol Bay through Kamishak Gap. A push of warm air will
keep the Eastern Aleutians and AKPen as mostly rain. From Pilot
Point north of Iliamna, precipitation may start as snow but there
will be a quick transition to all rain as the front approaches.
From Dillingham to Koliganek and areas north and west will see a
longer period of snow and blowing snow, starting this evening and
persisting into Tuesday morning before switching to rain. Wind
gusts as high as 60 mph will promote areas of blowing snow and
reduce visibilities to one-half mile. Dillingham to Koliganek can
expect to see snow accumulations of up to 5 inches with higher
amounts likely at higher elevations. A Winter Weather Advisory is
now in effect to highlight these impacts. All areas across Bristol
Bay will transition to rain by late Tuesday morning.

There are two Blizzard Warnings in effect as well, one for the
Kuskokwim Delta, primarily areas west of Bethel with highest
chances along the coast from Kipnuk to Tununak and Nunivak Island.
Snow amounts along the coast of up to 9 inches, with decreasing
values further inland near Kasigluk. Bethel and areas east can
expect to see up to an inch of snow accumulation, and with northeasterly
gale force winds periods of blowing snow may reduce visibilities
to one-half mile or less a times. The Blizzard Warning is in
effect from late this evening to early Tuesday afternoon.

The second Blizzard Warning is for the Pribilof Islands beginning
this evening to Tuesday afternoon. Winds are expected to shift to
north- northeasterly as the low pushes towards Southwest Alaska,
pulling colder air over the Islands and dropping snow levels.
Temperatures will hover near or just above freezing, allowing for
a dense, wet snow. The combination of heavy snow and strong winds
will result in visibility reductions to one-quarter mile.

-KM

&&

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

A large low associated with the remnants of Kong-rey will remain
stationary just off the Kuskokwim Delta coast through the long
range period. Precipitation will be mostly in the form of snow
with a rain/snow mix in the coastal areas. Cold air advection will
slowly filter into Southwest Alaska through the period, which
will make any precipitation solidly snowfall in the Kuskokwim
Delta and Bristol Bay regions as the low remains in place. There
is some potential for coastal flooding in the Kuskokwim Delta
coastline near Kongiganak and Kipnuk on Thursday due to the high
tide and the low. However, with wind speeds of 25 to 30 mph, the
odds of flooding occurring is on the lower side.

A broad low will move into the Gulf of Alaska by Thursday. Gusty
gale force winds will affect Southcentral coastlines, especially
near Kodiak Island, the Barren Islands, and Kamishak Bay before
weakening on Friday. There is uncertainty with the track so the
winds may be weaker if the low takes an easterly track.
Precipitation across the Southern mainland coastline is expected
with this low. The coasts will see mostly rain with higher
elevations seeing mostly snowfall. Inland areas will be mainly dry
but if they receive any precipitation, it will be in the form of
light snow. Another broad low will impact Southern Alaska on
Sunday. There is even more uncertainty with the low, but models
show that it may be more impactful than Thursday's low. It will
bring strong gale force winds for the marine regions of Southcentral.
It will also allow for more heavy rains across the Gulf coastline
and snowfall further inland and at higher elevations. The end of
the period brings us back to the West, where another low passes
south of the Aleutian Islands in the north Pacific. Uncertainty
arises but this low may impact the Gulf in the future.

-JR

&&.AVIATION...

PANC...While snow has come to an end, IFR visibilities likely to
linger through the morning as saturated lower levels lead to areas
of fog and low stratus. Otherwise, MVFR ceilings will gradually
improve through the morning and early afternoon. As a front begins
moving in later today, expect LLWS due to strong
east/southeasterly winds aloft and lighter northerly winds at the
surface. Though downsloping due to strong easterly flow aloft
will help reduce precipitation intensity, the moisture associated
with this front is still expected to bring light precipitation
(snow transitioning to rain) on Tuesday morning.

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
633 AM AKST Mon Nov 4 2024

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

1235 AM     Snow             Butte                   61.53N 149.01W
11/04/2024  M1.3 Inch        Matanuska-Susitna  AK   Trained Spotter

0736 PM     Snow             Eagle River             61.32N 149.54W
11/03/2024  M1.0 Inch        Anchorage          AK   Trained Spotter

            At least 1 inch of snow accumulation.
            Snowing at observation.

1010 PM     Snow             NWS Office              61.16N 149.99W
11/03/2024  M0.5 Inch        Anchorage          AK   Official NWS Obs

            0.5 inches of snow measured. 0.07 in liquid
            equivalent. Snow depth 16 inches.

1030 PM     Snow             Russian Jack Park       61.20N 149.79W
11/03/2024  M0.5 Inch        Anchorage          AK   NWS Employee

            0.5 inches of snow since 4:30 pm. Estimated
            trace before that. Measurement may be
            underestimate due to above freezing temps.
            Not snowing at observation.

&&