Gale Warning 52, NWS Anchorage, AK

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

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

Conditions are rather tranquil across much of Southcentral this
morning with two pockets of shower activity, one over the northern
Gulf and a second across southern Cook Inlet. Elsewhere,
temperatures are starting out well below zero across the Copper
River Basin, where clear skies prevail. Farther west, morning
temperatures are holding steady in the teens and 20s as cloud
cover beings to slowly increase ahead of the next upcoming
frontal system setting its sights on Southcentral through Monday.

As mentioned, the next system to roll into our area will be a
strong frontal boundary originating from a low pressure system in
the Southern Bering. The front will enter the Southwestern Gulf
of Alaska this morning, bringing a brief period of snow to Kodiak
early this morning before a quick changeover to rain along with
Some showers will be generated in front 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 move slowly northeastward throughout the day
Saturday, with rain and strong winds for Kodiak Island through
early Sunday morning. The front will reach the Southern Kenai
Peninsula by early Sunday morning. Homer and Seldovia will likely
see an onset of a rain/snow mix but will change quickly to rain as
strong southeasterly winds usher in warmer air along the coast. A
similar evolution of the precipitation is expected for Whittier,
Portage, and Seward as cold air in place initially may lead to a
brief period of snow before warmer air moves in and changes the
precipitation to rain for the majority of this event.

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 from Turnagain Pass and the Hope Cutoff south to Moose
Pass will likely see 10 to 16 inches of snow, with the higher
accumulations for more inland areas such as near Summit Lake.
Several inches of snow could also fall from south of Moose Pass
to north of Bear Creek. However, with such a strong uptick in
east-southeasterly winds and recent model runs showing slightly
warmer air aloft, these areas may also see a transition to a
rain/snow mix that could reduce potential snow amounts. 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. Although, with temperatures warming to
around freezing, the extent of blowing snow will likely be
limited. By Sunday morning, the core of strongest winds ahead of
the front will make its way into Prince William Sound and through
Turnagain Arm. Wind gusts between 50 and 60 mph are not out of the
question from Portage to Bird Point Sunday morning. Similar gusts
will also occur along the highest peaks east of Anchorage;
however, given the overall pressure field, these stronger gusts
will likely stay out of the Anchorage Hillside, with this area
potentially seeing winds to 45 mph.

The Mat Valley will also see winds increase late Saturday into
Sunday morning as a result of the increased pressure gradient,
with gusts to 45 mph likely.

As the upper level trough lifts north and a surface low develops
near Seward along the front, snow will develop over Cook Inlet by
Sunday afternoon. This band of snow will move north over Anchorage
and the Mat-Su Valleys sometime between late Sunday evening and
early Monday morning; there are some timing issues yet to be
resolved in the models. Nonetheless, this set up looks eerily
similar to that of the previous snow event for Anchorage, Palmer,
and Wasilla. As such, snow accumulations of 2 to 4 inches by
Monday morning for these locations is not out of the question.

-TM/CL

&&

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

The forecast continues to look on track as a powerful storm system
moves into the Bering Sea and Alaska. Few changes were made to the
overnight forecast, though one major change was the issuance of
a Winter Weather Advisory for the Lower Kuskokwim Valley due to
high snow amounts. High Wind Warnings, Blizzard Warnings, Special
Weather Statements, and a multitude of marine weather warnings
remain in effect across the Bering Sea and Southwest Alaska. Check
out the latest warnings and forecasts for your local area at
weather.gov/afc.

Diving into the details, satellite imagery shows a 950 mb low
crossing into the Bering Sea near Nikolski, with its front
stretching towards the Alaska Peninsula and Southwest Alaska.
Strong winds were observed yesterday with the front, most notably
a 69 mph gust at Cold Bay. While most areas have seen conditions
improve behind the front, winds will ramp up through the morning
as cold air wraps around the low, leading to the 80 to even 100
mph winds advertised in the High Wind Warnings. As the front
approaches Kuskokwim Delta later this morning, strong winds and
falling snow will lead to blizzard conditions along the coast and
for Nunivak Island.

The potential for moderate to heavy precipitation with this system is
evident on satellite, where broad areas of the front have
observed precipitable water values of 0.90 to 1.00 inches. As
mentioned above, a Winter Weather Advisory is now in effect for
Lower Kuskokwim Valley, where 4 to 8 inches of snow are expected
from this afternoon through Sunday afternoon. This is a bit of a
marginal event, with snow expected to fall over a longer duration.
The primary areas of uncertainty here are precipitation amounts
and temperatures: how long will the front stall over the Lower
Kuskokwim Valley, and will temperatures stay cool enough for
precipitation to stay all snow? The current forecast leans on
higher precipitation amounts and on precipitation staying all
snow. As such, a shift towards a faster-moving front and higher
temperatures could easily lead to lower snow amounts.

In addition to the products in effect, there will be the
potential for higher water along the Kuskokwim Delta coast due to
strong onshore winds. Confidence is also fairly high that
temperatures will warm above freezing for much of Southwest
Alaska, climbing into the mid to high 30s. The southern portion of
Bristol Bay will likely see rain, but a rain/snow mix is also
possible as far north as Kuskokwim Delta and Lower Kuskokwim
Valley. Overall, an unpleasant and hazardous weekend is in store
for much of Southwest Alaska, the Bering Sea, and the Aleutian
Islands.

- KC

&&

.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 north to northeast winds less
than 10 kts will persist. Later this afternoon into 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 will be more impressive aloft
compared to what's been observed over the past few days, and this
may lead to a more appreciable threat for LLWS to develop at the
terminal late this afternoon that will persist into Sunday
morning.

-AS

&&