Small Craft Advisory 14, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
446 PM AKST Fri Jan 3 2025

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

Bitter cold temperatures continue over most of the Copper River
Basin and Thompson Pass today as an arctic airmass continues to
linger over Southcentral. Ambient temperatures in the lower
valleys of the Basin rain between 30 to 40 below zero, with wind
chills as low as 50 below zero. Temperatures near Thompson Pass
are in the negative teens, but gusty conditions are still
producing wind chills near 50 below zero. A Cold Weather Advisory
is still in effect for both location as a result of these cold
conditions.

A band of snow has formed over the western Kenai Peninsula this
afternoon and will expand northeastward towards the Anchorage
Bowl this evening. A couple of inches of snow have been reported
near Homer, and any future accumulations will be light.
Additionally, a wave of light snow is moving over the eastern
portions of Prince William Sound and will shift towards the
western Sound tonight before dissipating by Saturday morning.

Gusty conditions will continue to simmer down this evening as the
pressure and thermal gradient over the Talkeetna and Chugach
Mountains begins to weaken. With the gustier winds still present
though, ambient temperatures will remain considerably warmer than
surrounding areas, staying in the upper teens through tomorrow
afternoon.

By Saturday and continuing into Sunday, a weak trough is expected to
move north into the central Gulf towards the Southcentral coastline
and Kodiak Island. An additional band of rain/snow will accompany
the trough as it lifts northward, however, models continue to
struggle with the timing of this system. What does look certain is
that most of the Gulf coastal areas will likely see precipitation,
likely beginning as snow with a transition to rain as temperatures
warm.

The biggest concern will be a series of waves behind this initial
wave that move towards the Southcentral coastline Sunday night and
throughout the day on Monday. While there are significant model
inconsistencies on track and intensity, there is growing concern
of widespread and further enhanced precipitation for both the
coastline and portions of interior Southcentral. Continue to
follow for more updates as this system develops.

- BS/PP

&&

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

More active weather is on the way as several lows rotate out of
the North Pacific and across Southwest Alaska. For the Bering Sea
and Aleutian Islands, a shift towards less active weather as the
low and its front weaken, gradually giving way to northerly flow
and snow showers. A Cold Weather Advisory remains in effect for
Lower Kuskokwim Valley through tomorrow afternoon, with wind chills
tonight expected to dip even lower than they did this morning.
Here are the other hazards we're monitoring:

* Heavy to extreme freezing spray through Sunday, with the most
  dangerous conditions expected along the ice edge from Kuskokwim
  Bay north towards St. Lawrence Island.

* Potential for reduced visibilities in blowing snow for the
  Pribilof Islands (around late Saturday afternoon through
  evening) and along the Bristol Bay coastline from Dillingham
  through Togiak (around late Sunday morning through the
  afternoon).

* From Sunday night through Monday, potential for freezing rain as
  a warm and very wet weather system barrels into Southwest Alaska
  from the North Pacific.

Forecast confidence continues to be a bit lower than average as
models struggle with the various weather systems moving up from
the North Pacific on Sunday and Monday. Models have recently come
into better agreement that a warm and wet low will move towards
Southwest Alaska, bringing an end to the recent cold spell. As we
transition from the current cold air mass to a warmer one though,
there could be some freezing rain and mixed precipitation. Given
major shifts in recent model runs, it's difficult to say for now
how things will play out. Stay tuned as we continue to refine the
forecast.

&&

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

Very little change from yesterday with minor edits for timing.
High confidence in the major pattern shift but low confidence in
system tracks and precipitation amounts and types.

In the east the dominate pattern features a strong ridge of high
pressure over western Canada and a deep upper level low over the
Eastern Aleutians and AKPEN Peninsula. The upper level low will
gradually migrate back over the Bering Sea as the week progresses.
This will flatten out the trough which will allow several compact
surface lows with triple point fronts to impact the region
through the end of the forecast period. Cool, dry air will
continue over most of interior Alaska. Active weather occurring
across the Southern half of the state will bring successive strong
southerly winds with high moisture inflow across Southcentral
Alaska with several transient lows. They will bring fairly high
frozen precipitation amounts to the upper levels and mixed precip
at the lower levels as temperatures gradually rise to at or just
above freezing.

In the west, a strong low in the North Pacific South of the
Aleutians brings rains to the Western and Central Aleutians with
gale force winds and snow over the Bering into Tuesday and
Wednesday. This North Pacific low moves away from Alaskan waters
South of the Central Aleutians through Friday. Rain or rain and
snow mixed continue in the northeasterly gales that slowly
diminish over the Northern Bering through Friday.

Inconsistent model guidance is the real challenge in the upcoming
week. GFS and Canadian models do well in days 4 and 5. GFS
becomes the outlier in days 6 and 7 where the European and and
Canadian models seem to perform only slightly better.

DD

&&

.AVIATION...

PANC...VFR conditions will persist through the forecast period.
Northerly winds will persist through the night. High ceilings
with a broken cloud deck will move in tonight. The increased
mixing and cloud cover should limit the chances for radiational
fog and low stratus to develop tonight and tomorrow morning.

&&