Gale Warning 50, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 PM AKST Fri Jan 5 2024

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

Ongoing rain and snowfall across coastal Southcentral will
continue overnight tonight. Skies across interior Southcentral
will gradually clear overnight tonight, allowing for some colder
morning temperatures by Saturday. Generally, the period between
this evening and Saturday morning will be a reprieve before the
onset of the next upcoming frontal system entering Southcentral
later this weekend.

As mentioned, the next system to roll into our area will be a
strong frontal boundary swinging in originating from a low
pressure system in the Southern Bering. The front, pushing
northward, will enter the Southwestern Gulf of Alaska by Saturday
morning, bringing a wave of snow and rain to Kodiak Island by 6am.
Some showers will be generated ahead of the front and should
restart some of the snow/rain showers in Western Prince William
Sound around the same time. The lagging core of the frontal
boundary will shift northward throughout the day Saturday,
reaching Kodiak and ramping up rain and snowfall rates by late
Saturday night. Reaching the Southern Kenai Peninsula by early
Sunday morning, Homer and Seldovia will likely see an onset of a
rain/snow mix but will likely see a predominance of rain
throughout the day Sunday due to the warmer temperatures of
Kachemak Bay. Persistent snowfall is expected to continue into
Sunday where the axis of moisture aligns with the flow into
Western Prince William Sound, increasing snowfall potential in
that area. The axis of strong moisture transport will begin to
move over Eastern Kenai Peninsula by 6am Sunday, beginning the
period of moderate-to-heavy snowfall potential. Portions of the
Seward highway between Seward and Turnagain Pass will see
approximately 16 inches along the highway corridor, with higher
accumulations for more inland areas such as near Summit Lake.
Whittier will similarly see a prolonged period of cold
precipitation but due to the temperatures sitting at or just above
freezing, it is difficult to determine how much snow versus rain
will be received at the surface in the city. It is possible for
higher elevations of Eastern Kenai to see up to 3 feet of new
snowfall from Sunday morning to Monday morning. The period of
strongest winds are currently expected to arrive, and depart prior
to the arrival of heavy snowfall, limiting but not eliminating
the potential for blowing snow reducing visibility along roadways
Sunday.

By Sunday afternoon, there is the potential for some of the
snowfall to break through Turnagain Arm and push into the
Anchorage area. This feature is currently supported by the high
resolution models, but not picked up by the synoptic models, so
confidence is low. However, a wave a snowfall appears to arrive
Sunday afternoon increasing by Sunday evening. Period of strongest
snowfall would be overnight Sunday into very early Monday
morning. Snowfall may continue but diminish throughout Monday
morning, ending late Monday morning. Snowfall from this minor push
into Anchorage Monday may produce up to 1 to 3 inches of new
snow, with higher amounts on the hillside. Confidence regarding
this impact to Anchorage is still low so stay tuned, however
confidence regarding the strong snowfall event in Eastern Kenai
Sunday into Monday is high.

-CL

&&

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

Key Points:

* A large and powerful storm will cross the Aleutians into the
  Bering Sea tonight through Saturday, bringing widespread severe
  weather to the region through the weekend.

* Several Warnings have been issued with this afternoon's forecast
  updates. Check the latest warnings and forecasts for your local
  area at weather.gov/afc.

Overall, the forecast remains on track for this storm system.
As is typical with these deep lows, there has been some shift in
the track and depth of the low. The root cause seems to be a
complex series of short-waves embedded within the upper trough,
which leads to development of multiple centers and transfer of
energy from one center to another as the low is crossing the
central Aleutians early Saturday morning. At the surface, the low
initially takes the track expected yesterday, passing just east of
Atka. However, in response to the shift in upper low centers, a
new surface low forms to the east and passes just west of
Nikolski. As the low continues north into the southern Bering, it
now looks like the core of strongest winds will affect the Eastern
Aleutians. Cold air advection and associated increase in
instability will combine with pressure rises behind the low to
accelerate winds moving through the mountains of the Eastern
Aleutians. The initial south to southwest wind direction is also
favorable for some of the strongest winds to funnel through
Captain's Bay and Unalaska Bay, affecting the main population
center of the zone. Meanwhile, the shift in low track means high
winds look a little less favorable for Atka and Adak, with the
core of strongest winds staying to the south and east. However,
they are still in the vicinity of the bent-back occlusion, and
Adak in particular will see some of the colder and more unstable
air on the back side of the system. Lastly, the eastward shift now
brings some of the stronger winds eastward to the southern tip of
the Alaska Peninsula, where winds easily accelerate through the
many bays and passes. Thus, have issued a High Wind Warning for
Cold Bay west to False Pass.

Meanwhile, the frontal system looks a bit stronger as it reaches
Southwest Alaska, so have upped winds and precipitation amounts
across the region Saturday through Saturday night. There is high
confidence in blizzard conditions along the Kuskokwim Delta coast
tomorrow. Enough warm air will move in to cause temperatures to
rise above freezing with frontal passage, but the bulk of snow
will fall prior to any warm-up with temperatures in the upper 20s.
The occluding front will be slow to progress inland and weaken
across Southwest Alaska Saturday night. Bristol Bay will quickly
warm and see mostly rain. However, expect all snow in the
Kuskokwim Valley. The precipitation forecast is always a bit
tricky in there when there is lots of low level wind (and
upslope/downslope affects). It does look like there will be a
narrow band of moderate snow ahead of the front that sits
somewhere between Aniak and Sleetmute Saturday afternoon through
Saturday night. Would like to see more model consistency with
progression of front, but there is a chance a Winter Weather
Advisory will need to be issued for snow accumulation of 6 or
more inches in a small portion of the Kuskokwim Valley.

Gusty winds and showers will persist region-wide through Sunday,
with improving conditions as the low weakens and exits to the far
northern Bering Sea Sunday night through Monday. Another strong
Pacific storm looks like it will arrive along the Aleutians Monday
night. This storm will take a more westerly track, which could
confine the greatest impacts to the Aleutians and central Bering
Sea.

&&

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

The big weather-feature that will drive the systems in the long
term period will be an amplifying upper level ridge over mainland
Alaska. This ridge will begin to amplify over Southwest mainland
Alaska Tuesday and then move over Southcentral and the Interior
for Thursday and Friday. What this will entail is keeping the
storm track on the Bering Sea region for next week. There looks to
be another major low that moves through the central Bering Sea
Tuesday and Wednesday, but this strong upper level ridge will keep
that low farther to the west than the ones moving through the are
this week. This low will still bring strong winds the the Bering
Sea and the Kuskokwim Delta coast for Tuesday and Wednesday. The
warm upper level ridge and low being ushered by it into the
Chukchi Sea will bring above-normal temperatures for Southwest
Alaska for much of next week. Southcentral also looks to have
above-normal temperatures, however there will also be less cloud
cover for Southcentral which will allow for better radiational
cooling overnight. Since the ridge has such a warm core, it will
mitigate the night time temperatures and keep them from being as
cold as they were last week when skies cleared out.

Especially toward the end of next week there is increased
uncertainty to the details of what is likely to be another strong
low in the Bering Sea and impacting Southwest mainland Alaska.
What does look likely is that this system will remain over the
Bering Sea due to the strength and placement of the upper level
ridge over Southcentral. The Southwest mainland will see some
wind and a mix of both rain and snow depending on how the track
and strength of the low develops. The main thing that will need
to be watched is to see if this ridge does amplify to be as
strong as currently projected and if it can maintain its place
over Southcentral and the Interior of the state for most of next
week.

&&

.AVIATION...

PANC...VFR conditions and light northeast winds less than 10 kts
will generally persist. Shower activity continues to be present
across the Cook Inlet, but remains just out of Anchorage. This
should remain the case this evening, but can't rule out a light
snow shower across the area. Precip activity across the area will
diminish later this evening/overnight.

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1022 PM AKST Fri Jan 5 2024

AKZ161-061400-
Bristol Bay-
Including the cities of King Salmon, Dillingham, Naknek,
and Pilot Point
1022 PM AKST Fri Jan 5 2024

...STRONG WINDS THIS WEEKEND ALONG WITH SNOW CHANGING TO RAIN...

A powerful storm system moving into the Bering Sea will bring
another round of very strong winds to coastal and interior Bristol
Bay this weekend. Southeasterly winds will quickly increase
Saturday morning and remain strong through Sunday morning before
diminishing Sunday afternoon. For the Bristol Bay coast, expect
sustained winds of 30 to 45 mph with gusts up to 55 mph possible.
For interior Bristol Bay, expect sustained winds of 35 to 50 mph
with gusts up to 65 mph possible. The winds are then expected to
diminish by Sunday evening as the low lifts into the Bering
Strait.

A brief period of snow is likely Saturday morning. However,
temperatures will quickly warm into the mid to upper 30s as the
winds increase, changing any snow over to rain.

AKZ195-061400-
Pribilof Islands-
Including the city of Saint Paul
1022 PM AKST Fri Jan 5 2024

...STRONG WINDS THIS WEEKEND ALONG WITH SNOW CHANGING TO RAIN...

A powerful storm system moving into the Bering Sea will bring
another round of very strong winds to the Pribilof Islands this
weekend. Easterly winds will quickly increase late Friday night
becoming southeasterly through Sunday morning. Expect sustained
winds of 35 to 50 mph with gusts up to 65 mph possible. There may
be a brief lull in the strong winds late Saturday evening through
early Sunday morning before winds shift to the southwest and
increase late Sunday morning through Monday morning. Expect
sustained winds of 35 to 50 mph with gusts to 65 mph during this
second round of strong winds. The winds are then expected to
diminish through Monday evening as the low lifts into the Bering
Strait.

A brief period of snow is likely late tonight. However,
temperatures will quickly warm into the mid to upper 30s as the
winds increase, changing any snow over to rain.