Winter Weather Advisory 73, NWS Anchorage, AK

798 
WWAK41 PAFC 230305
WSWAER

URGENT - WINTER WEATHER MESSAGE
National Weather Service Anchorage AK
605 PM AKST Wed Dec 22 2021

AKZ121-230415-
/O.EXP.PAFC.WW.Y.0073.000000T0000Z-211223T0300Z/
Western Kenai Peninsula-
Including the cities of Kenai, Soldotna, Homer, 
and Cooper Landing
605 PM AKST Wed Dec 22 2021

...WINTER WEATHER ADVISORY HAS EXPIRED...

The areas of freezing rain have ended around the western Kenai 
Peninsula.

$$

http://www.weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 AM AKST Wed Dec 22 2021

.ANALYSIS AND UPPER LEVELS...

A ridge of high pressure remains draped across the western
Aleutians extending to Southcentral. A 165 kt southerly jet
streak is placed over the western Aleutians, while a 160 kt
northerly jet streak is located over Southcentral. Low- level
moisture remains trapped in locations over Southcentral.
Nighttime Microphysics is showing dense fog located over Ted
Stevens International Airport that is extending down through Cook
Inlet and north towards Talkeetna this morning. Higher-level
clouds continue to build into Southwest Alaska and move east
toward Southcentral ahead of the next storm system. The warm front
associated with this system is causing a variety of precipitation
type issues in the Southwest. Thus, Winter Weather Advisories are
in effect for those areas. See the short- term forecast for
Southwest for more information. Temperatures will continue to be
on the mild side with another warm front pushing through the
domain. Behind the warm front in the Aleutians, temperatures are
being reported in the 40s and 50s, while ahead of the front in
Southwest Alaska, temperatures are around the upper 20s to mid
30s. Southcentral is seeing similarly "warmer" temperatures with
Ted Stevens reporting in the upper teens this morning.

&&

.MODEL DISCUSSION...

Models remain in good agreement on the placement of the major
features. Some differences exist with the track of the low moving
north, placing it west of the high in the Western Aleutians.
However,there's good agreement on a large surface trough extending
along the Gulf coast into Prince William Sound. The main points
of uncertainty are the timing of precipitation type changes across
Southwest Alaska today and also the duration and placement of fog
across Southcentral. Overall, forecast confidence is average.

&&

.AVIATION...
PANC...IFR to LIFR conditions continue over the terminal due to
widespread fog, with little to no wind to help to scatter it out.
The fog may move around locally and can cause large fluctuations
in visibility at times. Increasing middle and upper level cloud
cover this morning should disrupt the fog- development process,
which should allow ceilings to return to MVFR, with VFR visibility.
Snow showers may impact the terminal this afternoon, but they are
expected be light and intermittent and will not result in
prolonged lowering in visibility.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2:
Today through Friday)...

Low stratus and areas of fog persist this morning across northern
Cook Inlet, the Anchorage Bowl and portions of the Susitna Valley.
The low ceilings and fog should continue to erode through the
morning hours as the low-level inversion weakens with the upper-
level ridge moving east in advance of a frontal system currently
over Southwest Alaska.

The front will quickly occlude and begin to weaken as it runs up
against the Alaska Range to the west. Nonetheless, warmer air
aloft ahead of the frost will still push across southern Cook
Inlet and the Kenai Peninsula just as precipitation is expected
to develop. Thus, any light snow developing across the Kenai
Peninsula later this morning will likely mix with sleet and
freezing rain, especially from Ninilchik south to Homer. The
bigger question is just how much precipitation develops across the
Cook Inlet region. Unlike the previous storm system, there is
less moisture associated with this system. Moreover, winds aloft
are more westerly and the shortwave associated with this feature
is positioned farther north. These differences will keep the best
upper-level dynamics and lift over interior Southcentral while
also preventing any additional moisture from the western Gulf from
moving northward. Still, given the robust nature of the feature
currently, thinking Homer to Anchorage will see some light
precipitation through Wednesday afternoon. Given the factors
listed above, less than half and inch of snow is expected from
Homer to Anchorage, with the potential for trace amounts of
sleet/freezing rain around Homer. Farther north, an inch of two
of snow is possible from Palmer to Talkeetna.

This shortwave will continue to move east tonight, with light
snow developing across the Copper River Basin and minor
accumulations of 1 to 3 inches possible.

The bigger story with this system will be the development of a
surface low over the northern Gulf by Wednesday evening. This
feature, coupled with the exiting shortwave, will help to drive
another round of cold air advection and strong gap winds along
coast late Wednesday through Thursday. Winds will wane slightly
Thursday afternoon, but are expected to ramp up again late
Thursday into Friday as a second shortwave moves south and
reinforces the cold air advection.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Wednesday
through Friday)...

A warm front is on approach to the Southwest coast this morning
with temperatures across the Kuskokwim Delta and Bristol Bay
already beginning to warm. Mixed precipitation in the form of
rain and freezing rain extends across the entirety of the
Kuskokwim Delta as buoyant warm air aloft helps to push much
colder air at the surface, eastward. This is temporarily allowing
rain to fall into a shallower layer of colder surface temperatures
resulting in the mix of precipitation types. On radar a narrower
band of precipitation currently stretches into north-central
Bristol Bay. For most areas across Southwest accumulations will be
minor with local amounts of up to a tenth of an inch of ice
accumulation possible. The exception will exist across the Lower
Kuskokwim Valley where more meaningful snow accumulations are
forecast, primarily east of Sleetmute. Here temperatures will be
slower to warm and upslope flow into the Alaska Range is likely to
result in heavier snow at times. By this even rain will taper off
from west to east, giving Southwest a small period of clearing.
Thursday will bring renewed snow chances across the region as a
shortwave trough moves into the Lower Kuskokwim Valley and
northerly winds on the backside of the trough see colder
temperatures return southward. By Friday a new area of low
pressure is forecast to lift into Southwest with another warm-up
possible. Numerical guidance suggests that Southwest will remain
in this pattern into next week as high pressure over the North
Pacific continues to drive upper-level disturbances further north
across Alaska, allowing for southerly winds to bring in warmer
air.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Wednesday through Friday)...

High pressure ridge will rebuild into the southern Bering over the
next couple of days bringing widespread stratus but dry
conditions across the Eastern Aleutians and Alaska Peninsula. To
the west, a steady southwest flow across the Western Aleutians
will bring several low pressure systems into the Bering over the
next couple of days. Warmer temperatures will keep precipitation
in the form of rain. Otherwise, small craft to gale southerly
winds will be confined largely to the western and central Bering
until Friday with the arrival of the next upper low.

&&

.MARINE (Days 3 through 5 - Friday through Sunday)...

Bering...Two well developed North Pacific lows track over the
Western Bering into the Russian Far East through Sunday. Widespread
gusty winds with areas of gales move across the Aleutians and
Bering, diminishing Saturday. Seas to 20 feet along the Pacific
side of the Aleutians, subsiding Saturday. The second North
Pacific low is stronger, with widespread high end gales and areas
of storm force winds over the Western and Central Bering for
Saturday and Sunday. Seas building to 28 feet on the Pacific side
of the Aleutians, and 23 feet over the Bering through Sunday.

Gulf of Alaska... Low pressure over the Eastern Gulf weakens with
a trough across the Northern Gulf through Sunday. Forecast
confidence is moderate with the rates of pressure changes over the
Gulf. Widespread gales extend from the Alaska Peninsula into the
Western Gulf, with the strongest winds over the Barren Island into
the Gulf, diminishing Saturday. Seas to 20 feet over the Western
Gulf, subsiding Saturday.

&&

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

A broad, stagnant Omega Blocking pattern is expected to dominate
the forecast area from west to east through the long term. The
center of the upper high will remain anchored over the central
North Pacific, while the ridge axis connected with the Omega Block
runs from the North Pacific through the eastern Aleutians/Bering
on Saturday before marching over Southwest Saturday night then
gradually reaching Southcentral between Monday night and Tuesday
morning. This could lead to warmer temperatures across Southwest
Alaska. Southcentral will be cooler with respect to temperature
than Southwest as Southcentral will be east of the ridge-axis and
thus allowing for northwesterly synoptic flow across the region.
Furthermore, strong subsidence east of the ridge-axis will allow
for mostly sunny skies by day and mostly clear skies and light
winds during the night. This will allow for cold nights across
Southcentral, especially in the Copper River Basin due to ideal
conditions for radiational cooling. That said, this is also a
pattern which can produce widespread foggy conditions due to the
subsidence. That may be the biggest forecast challenge in the
long-term period.

Warm southwesterlies across Southwest Alaska will enhance plumes
of moisture across the region. The precipitation-type remains a
forecast challenge as precipitation transits through Southwest. Warm
air advection will allow for a mix of precipitation-types. Chance
of rain could be favorable along the lower lying coastal areas
while the potential for chance of snow will be further inland
areas such as the lower Kuskokwim Valley and in the Kuskokwim and
Alaska Ranges.

Though global models share similar synoptic features for the long
term, clearly GFS and ECMWF display a lot of similarities
especially in keeping the ridge-axis in motion through
Southcentral by Tuesday. While GEM maintains a delayed forward
motion of the ridge throughout the forecast period.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 152 155 161.
MARINE...Storm 131 351
         Gale 119-121 125 129 130 132 136 138 139 141 177 178 180
              181 185 352 411-414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...NS
SOUTHCENTRAL ALASKA...TM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BL
MARINE/LONG TERM...MK/CB

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
531 AM AKST Wed Dec 22 2021

AKZ121-230300-
Western Kenai Peninsula-
Including the cities of Kenai, Soldotna, Homer,
and Cooper Landing
531 AM AKST Wed Dec 22 2021

...A LIGHT WINTRY MIX OF PRECIPITATION POSSIBLE SOUTH OF KENAI
WEDNESDAY...

Light wintry precipitation is expected to overspread the western
Kenai Peninsula Wednesday morning as a frontal system advances
from the west. As the front moves east, an area of warmer air
aloft will move across southern Cook Inlet and the western Kenai
Peninsula. With temperatures at or below freezing at the surface,
any light snow initially may mix with or changeover to sleet and
freezing rain. Any precipitation is expected to be light, with
less than half an inch of snow and trace of ice accumulation
possible. The best chance for any mixed precipitation will be from
Ninilchik south to Homer. There is also a slight chance that any
precipitation that falls along the western Kenai Peninsula coast
may end as a brief period of freezing drizzle as clouds linger
along Cook Inlet Wednesday evening before diminishing Wednesday
night.