High Wind Warning 17, NWS Anchorage, AK

307 
WWAK71 PAFC 061447
NPWAER

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
547 AM AKST Wed Dec 6 2023

AKZ171-061600-
/O.EXP.PAFC.HW.W.0017.000000T0000Z-231206T1500Z/
Kodiak Island-
Including the city of Kodiak City
547 AM AKST Wed Dec 6 2023

...HIGH WIND WARNING WILL EXPIRE AT 6 AM AKST EARLY THIS
MORNING...

Winds have dropped below high wind warning criteria, therefore the
warning has been allowed to expire. Winds will continue to 
subside across Kodiak Island through the day. 

$$

For more information from the National Weather Service visit
https://weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 PM AKST Tue Dec 5 2023

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

A broad region of low pressure south of Middleton Island will
slowly consolidate as it moves towards Prince William Sound
through Wednesday. Meanwhile, an upper level trough will take on a
negative tilt as it moves east through early Thursday morning. The
combination of these two features will generate a deformation band
and light to moderate snow from the Mat Valley south through
Anchorage and into the Kenai Mountains. To the east, the surface
low and associated lift will bring periods of snow to the southern
and central Copper Valley, Valdez, and eventually Cordova late
Wednesday as colder air wraps in from the west. As mentioned in
previous discussions, there has been considerable model
disagreement, but all the solutions have moved towards that of the
GFS and ECMWF. As such, there is a 60-70% chance that Anchorage
and areas of the Mat Valley will get 2-5 inches of snow, with up
to 8 inches at higher elevations along the Hillside. Much lower
accumulations are still possible should the area of deformation
set up farther to the east. The GFS solution continues the snow
and deformation for a longer period of time, which would result
in up to 12 inches in areas, but current forecast thinking is that
the cold air advection on the backside of the system should be
enough to kick the parent trough farther to the east.

Winds associated with this system will remain strong for at least
the next 24 hours through Whittier, Seward, and Thompson Pass.
Intermittent snow through Thompson Pass in combination with winds
gusting 40 to 60 mph will produce blizzard conditions at times.
For Whittier, temperatures hovering between 28 and 32 degrees may
be too warm to produce true blizzard conditions, but residents
there should prepare for the possibility. Seward is not expected
to receive enough snow for blizzard conditions, but strong and
gusty winds will persist.

Moving into Thursday there will be little break in between
systems. A deep upper low near Norton Sound will bring in strong
cold air advection from the southwest, generating a low at the
triple point south of the Kenai Peninsula Thursday around midday.
The trough will then take on a negative tilt as the surface low
advances into the western Prince William Sound Thursday evening.
Expect widespread light to moderate snow down to sea level
throughout all of Southcentral. Temperatures aloft will cool
considerably, down to -10 to -16C at 850mb, which will generate
low density snow.

-Jones

&&

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

A look at the large scale pattern shows a deep mature low in the
Gulf of Alaska and a flattened ridge over the Aleutians/southern
Bering Sea with a deep upper low and trough tracking out of eastern
Russia and into the northern Bering Sea. Strong northwesterly gap
winds are being observed along the south side of the Alaska Peninsula
due to strong pressure gradients and cold air advection. A weak
upper level short-wave will cross the northern Peninsula late this
afternoon into evening, which is when winds will peak in the
coastal waters immediately south of Kodiak Island. Winds will then
diminish later this evening, but there will be another uptick in
winds for this area overnight through early Wednesday as a weak
short-wave and reinforcing shot of cold air move through. However,
winds will not be nearly as strong as today. Gap winds will then
come to en end by late Wednesday afternoon as flow backs around
toward the west to southwest ahead of the low crossing the
northern Bering Sea. There will be some freezing spray along the
south side of the Alaska Peninsula tonight through Wednesday
morning, but SSTs are still relatively warm (lower 40s) and air
temperatures are not all that cold (mid to upper 20s), so the
freezing spray will be light.

Meanwhile, a showery regime will prevail across the Bering Sea,
Aleutians and Southwest Alaska for the next few days. While there
are currently some weak upper short-waves crossing the eastern
Bering Sea and Southwest Alaska, the main weather maker will be
the storm system crossing the northern Bering. A strong upper
level short-wave on the back side of the low will dig southeastward
across the Bering Sea Wednesday and across the Alaska Peninsula
into the Pacific Thursday. Arctic air will accompany the trough
southward, with 850mb temperatures bottoming out at roughly -12 to
-18 degrees for most of the region on Thursday. There will be
periods of blowing snow with low visibilities for coastal areas.
Because of the showery nature of the precipitation, visibility
will tend to go up and down with only brief periods of the worst
conditions. Temperatures will steadily trend downward over the
next few days as the Arctic airmass settles in. Based on the track
of the upper level short-wave and area of strongest cold air
advection, weather along the Aleutian chain will be a little
quieter, with less where activity and less wind compared with
other areas.

&&

.LONG TERM FORECAST (Days 4 through 7)...Saturday through Tuesday...

In the West, high pressure extends into the Russian Far East,
bringing gale force winds to the Western and Central Aleutians.
The main axis of the longwave trough over the Eastern Bering and
Western Alaska wobbles and briefly reorients as a number of
significant shortwaves rotate through the region. A closed center
in the middle of the trough weakens as it drifts slowly around the
Southwestern Mainland through Tuesday. Forecast confidence is
mixed as deterministic models work initially, but ensembles work
through the end of the forecast period. Colder air with the trough
helps keep most precipitation as snow showers over the Aleutians,
Bering and the Mainland Alaska. Locally heavy rains invade the
Southern portions of the Alaska Peninsula, Kodiak Island and
Southcentral, as Pacific lows are deflected into the Gulf. Gale
force gap winds, with local areas of storm force winds spread from
the Eastern Aleutians, over the AKPEN and around Kodiak Island.

Additional moisture from a North Pacific low as it comes close
along the Eastern Aleutians and Alaska Peninsula Monday and
Tuesday. Locally heavier precipitation spreads eastward with the
low's track, along with gale force winds. As the lows move into
the Gulf, the Eastern portions of Southcentral could see heavier
periods of precipitation, and locally gusty winds approaching
gales for Tuesday.

Kutz

&&

.AVIATION...

PANC...PANC...VFR ceilings with sct to bkn 5-10 kft deck will
gradually fill in and lower overnight with MVFR and possible IFR
deck by 12- 15Z. A round of light snow is expected to spread into
the terminal Wed morning with periodic decreases in visibility
through 21-00Z.

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
514 PM AKST Tue Dec 5 2023

AKZ171-061500-
Kodiak Island-
Including the city of Kodiak City
514 PM AKST Tue Dec 5 2023

...RESUSPENDED ASH FROM KATMAI-NOVARUPTA EXPECTED OVER KODIAK
ISLAND TUESDAY EVENING THROUGH WEDNESDAY EVENING...

Strong northwesterly winds of up to 50 mph across the southern
coast of the Alaska Peninsula and Shelikof Strait will continue
through Wednesday evening. These winds will resuspend ash from
the 1912 Katmai-Novarupta eruption. The villages of Karluk and
Larsen Bay are most likely to be impacted.

Those with respiratory ailments in these areas are encouraged to
avoid or reduce outdoor activity to avoid inhaling the ash. The
winds are expected to diminish and shift to the west-southwest by
Wednesday evening, which would allow any lingering ash to move
away from Kodiak Island and settle out of the atmosphere.