Small Craft Advisory 22, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 PM AKST Sat Jan 6 2024

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

The active pattern for the Gulf coast is continuing with ongoing
showers along the southern and eastern side of Kenai Peninsula.
Precipitation with these showers continues to be variable and
difficult to keep up with as snow is falling at 35 degrees in
places like Whittier and Portage. Accumulation rates regarding the
ongoing showers are relatively low, due to the lack of ample
moisture and near freezing temperatures near the surface in these
coastal locations. This however is liable to change soon as a
large and strong frontal boundary is approaching Southcentral from
the southwestern Gulf of Alaska. While the axis of highest
moisture content isn't expected to reach Kodiak Island until
around midnight, moisture and winds ahead of the front will be
moving into the northern Gulf by before midnight tonight. Near
Kodiak City, moderate to heavy rainfall will be strongest before
midnight, diminishing through the morning, and coming to an end as
the front departs to the north by late Sunday morning. Near
Kodiak, up to 1 inch of rainfall is expected with the passage of
this system. Snow and rain regimes across the Southcentral
coastline will intensify overnight as the core of strongest
moisture content approaches.

Winds ahead of the front will increase throughout the night, with
the strongest winds along the mountain tops of Southern Kenai
Peninsula reaching 85 mph, hurricane-force, gusts very early
Sunday morning. Winds will similarly increase across the Western
and Central Chugach ranges tonight into Sunday morning reaching up
to 65 mph. These strong winds at elevation are expected to
continue for much of the day Sunday, diminishing Sunday evening.

The main forecasting question in the short-term is how much snow
we get in the valleys of the Eastern Kenai Peninsula and eastern
Turnagain Arm, due to the fickle nature of snow versus rain at 35
degrees. For Whittier and Portage, an snow-to-rain-back to snow
pattern is likely Sunday with some easterly wind potentially
bringing in some temperatures slightly above 34. Snow
accumulations currently expected be up to half a foot, with more
on the surrounding elevations. Near Seward, warmer air pushing in
from the front will likely keep the city warm enough to see all
rainfall with the passage of this system. Then between Bear Creek
and Turnagain Pass will be near freezing and potentially sheltered
by the surrounding terrain. Currently, 2 to 5 inches of new snow
is expected on the Seward highway stretch from Bear Creek to Moose
Pass, while 12 to 22 inches are possible along the roadways
through Turnagain Pass to the Hope Cutoff. Period of highest
snowfall intensity expected to be near 9 am Sunday morning.
Snowfall will diminish, but continue across Western Prince William
Sound and the Kenai Peninsula coming to an end fully potentially
by Midnight Tuesday morning.

For Anchorage, confidence has grown towards the solution of a
quick shot of snow coming to Anchorage by Sunday afternoon. While
this is likely to be quick event, it is expected to be a fairly
intense snowfall rate, dropping about 3 to 6 inches across the
Anchorage area, with higher accumulations on the hillside. Period
of strongest snowfall likely to be just after midnight Sunday
into early Monday morning. Snowfall may continue but diminish
throughout Monday morning, ending late Monday morning.

Beyond this frontal boundary, Southcentral does seem to enter a
fairly quiet period, as weak ridging looks to move in beginning
Tuesday. This may provide a break from the active weather across
the Southcentral coastline, but may lead to some colder overnight
temperatures in the Copper River Basin. We will continue to
monitor the active weather pattern, and look forward to the
potential break.

&&

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

The third powerful low of the week is centered it the Bering Sea
near the Pribilof Islands this afternoon. An occluded front is
wrapped around this low and enhancing the winds over the Central
and Eastern Aleutians where high wind warnings remain in effect
into this evening. Rain is the predominant precipitation type of
the Bristol region southwest across the Alaska Peninsula and into
the eastern Aleutians. Colder air from the northwest has moved
into the central Aleutians bringing in snow and blowing snow from
Atka westward with brief blizzard conditions in Adak. The warmest
air has moved into Bristol Bay this afternoon where places like
King Salmon have had temperatures in the mid 40s due to the warm
air and adiabatic compression in the downslope winds. Above
freezing temperatures have made it to the Dillingham and Bethel
areas as well. The Kuskokwim Valley is the area that is expected
to hold onto snow as its primary precipitation type with more
northern areas of the region (such as near Sleetmute) seeing
significant snowfall accumulations through tomorrow morning
necessitating the winter weather advisory for that area.

As this low moves slowly northward and weakens over the two days,
the winds will diminish and and precipitation type will mainly
taper off to snow showers across the area as the colder air
filters into the system. The next large low will move into the
Aleutian Islands region Tuesday night into Wednesday.

&&

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

The main long-term weather feature will be an amplifying upper
level ridge over mainland Alaska. This ridge will strengthen over
Southwest mainland Alaska Tuesday and then move over Southcentral
and the Interior on Thursday and Friday. This will keep the storm
track over the Bering Sea region next week. Another major low
looks to move through the central Bering Sea Tuesday and
Wednesday, but the upper level ridge will keep that low over the
central Bering and western coastal zone. This low will still bring
strong winds the the Bering Sea and the Kuskokwim Delta coast
Tuesday and Wednesday. The warm upper level ridge will usher the
low into the Chukchi Sea and will bring above-normal temperatures
to Southwest Alaska for much of next week. Southcentral also looks
to have above-normal temperatures, however there will also be
less cloud cover across Southcentral which will allow for better
radiational cooling overnight. Since the ridge has such a warm
core, it will moderate some of the nighttime cooling.

Toward the end of next week uncertainty increases on the details
of what is likely to be another strong low entering 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 questions to answer will be to see if this
ridge amplifies to be as strong as currently projected, and if it
will maintain its placement over Southcentral and the Interior of
the state for most of next week.

&&

.AVIATION...

PANC...VFR conditions and light winds less than 10 kts will
persist into tonight. Tonight, a strong frontal system will
approach the southern Kenai Peninsula as winds once again pick up
out of the southeast aloft ahead of this feature. Southeast winds
ahead of the front will be more impressive aloft compared to
what's been observed over the past few days at the surface. This
has lead to the a more appreciable threat for LLWS to developing
at the terminal late this evening that will persist into Sunday
morning.

Downsloping winds (And the resultant LLWS) will slacken after 00z
Monday, allowing for snow to fill back into the Anchorage area. A
quick-accumulating 2-4 inches is most likely for PANC in that
00z-12z Monday timeframe. Light snow /flurries may linger
thereafter, but no substantial accumulation expected.

-CC

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
127 AM AKST Sun Jan 7 2024

AKZ102-072100-
Anchorage-
Including the cities of Anchorage, Eagle River, Indian,
and Eklutna
127 AM AKST Sun Jan 7 2024

...STRONG WINDS ACROSS THE ANCHORAGE HILLSIDE AND TURNAGAIN ARM
THROUGH SUNDAY MORNING...

A powerful frontal system moving into the northern Gulf of Alaska
Sunday afternoon will bring strong winds through Turnagain Arm and
across the Anchorage Hillside through Sunday morning. Sustained
winds of 25 to 40 mph are possible with gusts up to 65 mph. The
strongest winds gusts will likely be along the Upper Hillside
around Glen Alps and through Upper Potter Valley. Gusts to 65 mph
are also possible along Turnagain Arm from Bird Point to Potter
Marsh. The peak of the strongest winds is expected between 3 AM
and 9 AM. Winds are then expected to quickly diminish through
Sunday afternoon with snow developing for Sunday evening through
early Monday morning.