Brisk Wind Advisory 8, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 AM AKST Sat Jan 27 2024

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

A more active weather pattern for southcentral Alaska is
beginning to get underway. GOES water vapor imagery shows an
upper-level trough across much of mainland Alaska, with unsettled
weather across the North Pacific and eastern Gulf of Alaska. The
coldest air of the season has filtered into much of the area, with
below 0 temps being recorded for just about everywhere in
southcentral Alaska outside of the immediate coastal areas. As of
5am, much of Anchorage, the Kenai Peninsula, and the Mat Valley
are observing in the range of -10 to -20 degrees Fahrenheit.
Farther north from Willow on up, -20s to around -30 are the norm
this morning. Easily the cold morning of the season thus far.

Temps are a bit warmer towards the Copper River Basin as cloud
cover has spread across the area in southerly flow ahead of the
longwave trough. The first of a series of waves has brought some
precipitation to the eastern Copper River Basin / eastern Chugach
/ eastern Wrangells. The next wave is still forecast to come in
tonight a bit farther west. Unfortunately there is still lots of
uncertainty with the path. Operational GFS and ECMWF, along with
many of their supporting ensemble members, have warning-level snow
for the southern Richardson Highway. Meanwhile, several other
models keep precip just off to the east. This will continue to be
watched closely today.

By late Sunday into Monday, high uncertainty for the fate of the
third low moving into the coast persists. A deep low will move
north into the Gulf ahead of the main trough beginning to pivot
east towards the Kenai Peninsula. Model spread remains fairly
large and in westernmost track scenario, the main low could move
all the way west into the Kenai Peninsula or western Prince
William Sound. This would result in heavy snowfall for the
mountains and areas around the Prince William Sound, coastal
Kenai, Kenai Mountains, and most places along the Seward Highway.
Anchorage, western Kenai, and Mat Valley will continue to be a
tricky forecast as the exact low track will determine the degree
of downsloping, and ultimately the amount of precip/snow.

&&

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

A strong upper-level ridge situated over the Bering Sea continues
to promote clear skies and cold northerly flow through Southwest
Alaska. Clear conditions across Southwest, in addition to a
northerly push of gusty cold winds from Interior Alaska, have made
for extremely cold temperatures with wind chills observed below
minus 40 this morning. Thus, a Wind Chill Advisory remains in
effect for the Lower Kuskokwim Valley, Kuskokwim Delta, and
Bristol Bay through Sunday morning. With the cold air advection,
winds could become gusty through susceptible terrain gaps. Wind
chill temperatures over much of Southwest is likely to remain in
the minus 40 to minus 50 degrees Fahrenheit range. In the lower
Kuskokwim Valley wind chill temperatures may reach minus 50 to
minus 60 Fahrenheit. Heavy freezing spray over Bristol Bay, the
Eastern Bering and the Southern marine side of the Alaska
Peninsula will consequently will see ice accretion of at least 4
cm per hour near the ice edge in the eastern Bering beginning as
soon as early this morning, potentially lasting into next week.
Temperatures will gradually rebound early to midweek next week as
an upper-level ridge builds from the North Pacific.

As cold air moves over relatively warmer sea surface temperatures
and winds increase from the north, ocean effect snow showers
have developed across the Bering Sea and are becoming more
prominent. A more defined organized system is spinning up in the
northwestern Bering and drop quickly toward the Pribilofs tonight.
This compact low pressure system will bring a quick round of
heavy snow and strong northeasterly winds gusting as high as 35 to
45 mph. Gusty winds combined with heavy snowfall may reduce
visibility to one mile or less at times due to blowing snow. The
worst conditions will be brief, likely lasting around 3 hours late
Saturday night. The system will track into the southeastern
Bering Sea through Sunday afternoon, bringing with it winds
gusting as high as 45 mph to the Eastern Aleutians.

&&

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

The longer term begins with a highly amplified and negatively
tilted trough extending from the Bering Strait to the western Gulf
of Alaska. This trough is expected to lift over Southcentral by
mid-week, with more of a zonal flow developing. The negative tilt
to the trough, however, lends to active weather with interior snow
and coastal rain for much of Southcentral through the first half
of next week. While uncertainty remains in the timing of the
upper-level trough passage, most deterministic and ensemble runs
show a low moving either over the Kenai Peninsula or into Prince
William Sound Monday night. While the surface low weakens Tuesday,
troughing and moisture advection remains over coastal Southcentral
through midweek. At this point, the GFS and GEFS looks the
outlier, keeping the trough in place and bringing yet another
surface low to Prince William Sound. The EC and GEM keep any
significant surface features well to the east. Whatever the
midweek evolution, it looks more likely that well below normal
temperatures will remain over Southwest Alaska well into next
week. For Southcentral, significant snowfall is beginning to look
more likely for the Kenai Peninsula north across the Anchorage
Bowl and Mat-Su Valleys beginning Monday. With this more westerly
track of surface features, precipitation will likely mix with and
change to rain along the coast by Monday, but may change back to
snow as the low moves north and colder air wraps back over the
Gulf and Southcentral coast by Tuesday.

-TM

&&

.AVIATION...

PANC...VFR cigs and vsbys expected through the TAF period. Winds
will remain from the N to NE between 4-8kts with upper level BKN
to OVC deck developing through the afternoon.

&&