Winter Storm and Winter Weather in Alaska, November 11 to 13, 2023

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
509 AM AKST Sat Nov 11 2023

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

The upper level low is finally drifting into the Gulf of Alaska
early this morning. this is pulling the last remaining areas of
light snow over the southern Kenai Peninsula with very little
additional accumulation expected. There will be a little rain
along the coast near Cordova with a weakening surface low east of
there, but otherwise partly to mostly clouds skies for most of
Southcentral today. An upper level ridge will build over the area
tonight into Sunday and should bring clearing to much of the area
before the hammer drops on the other side of that ridge. That
hammer is in the form of a fairly strong front that will move over
Southcentral from west-to-east Sunday evening through Monday
evening. There is a lot of moisture in the due-south flow aloft
with this system which should bring snowfall to most of the
region. A difference with this system and the ones plaguing
Southcentral for much of this past week is that, being a front,
it will sweep through fairly quickly and not linger over the
region. That said, there will be some rather good snowfall rates
during as the front is going through.

The there are two notable questions in regards to this system. the
first revolves around the potential for a transition to rain
around the Kachemak Bay area early Monday. The second is the wind
direction around Anchorage Sunday night and Monday morning as
this goes through. With the GFS is keeping winds northerly, the
NAM is bringing the winds from Turnagain Arm over Anchorage. While
this typically produces precipitation-type concerns for Anchorage,
this system looks plenty cold enough to remain all snow even if
there is Southeasterly winds. What southeasterly winds could do is
cause a convergence zone to occur over west Anchorage which would
put heaviest snowfall amounts in west Anchorage and lesser
amounts in east Anchorage and especially Eagle River. This wind
direction is one of the bigger items to sort out as this system
approaches.

&&

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

The short term forecast remains largely on track with minimal
changes made. A large upper-level low exits from Southwest Alaska
into the Gulf today as a high amplitude ridge builds in from the
west. Across the Southwest coast and out into the eastern Bering
Sea, widespread strong and gusty winds (gale force over the marine
areas) and snow showers will continue through this morning. These
will extend southward to Unalaska and the Alaska Peninsula, with
some rain mixing in due a shallow layer of warm air near the
surface. Showers and winds will linger longest along the Alaska
Peninsula. A warm front right on the leading edge of the ridge
will produce a band of rain from the Pribilof Islands south to the
Eastern Aleutians and southern Alaska Peninsula today. This front
will dissipate before it reaches the Southwest mainland.

Further to the west, a storm force low will track northward
across the far western Bering today and then all the way up into
the Russian Arctic on Sunday. Its surface front will lift eastward
across the Bering and Aleutians Saturday night before pushing
inland across Southwest on Sunday. Conditions will initially be
cold enough for snow as precipitation first arrives, but much
warmer air aloft will lead to a quick transition to rain for the
Kuskokwim Delta and coastal areas of Bristol Bay. A brief period
of light freezing rain is possible Sunday morning into the early
afternoon during the transition from snow to rain. Any ice
accumulations are most likely to be trace to a few hundredths of
an inch. Precipitation will spread across interior Bristol Bay and
Lower Kuskokwim Valley later on Sunday and will most likely
remain snow, although a brief period of mixed precipitation is
possible near Aniak early Sunday afternoon. By Sunday night, much
colder air behind the front is expected to turn any remaining
precipitation to snow. The combination of cold air advection and
short-waves rapidly tracking eastward across the Bering Sea will
bring a showery regime to the Bering, Pribilof Islands, and into
Southwest Alaska for Monday.

With continued progressive flow aloft, another storm system will
track from the Pacific to the Aleutian chain Monday, with gale to
storm force winds likely over the coastal waters. Much warmer air
aloft will accompany this low, ensuring balmy surface temperatures
and a precipitation type of all rain. The system's low center will
track across the Bering on Tuesday while its front extends out
ahead of it and reaches Southwest Alaska by Tuesday evening.

&&

.LONG TERM FORECAST (Days 4 through 7)...

A very progressive weather pattern will continue into and through
the extended range forecast period with multiple strong
shortwaves riding over a strong but broad ridge over the Northern
Pacific Ensemble means confidence improves by Thursday. The broad
longwave ridge moves across the Southern Mainland through
Thursday. A well developed shortwave trough approaches Bristol Bay
for Wednesday and moves across the Gulf of Alaska through
Thursday. Gale force winds and locally heavy precipitation will
occur from Western Alaska and the Alaska Peninsula with potential
coastal flooding and strong winds. Gales will continue around
Kodiak Island and over the Southern end of the Kenai Peninsula
through Wednesday. Areas of heavy snow for the Alaska Range and
parts of the Kuskokwim Valley. Widespread precipitation is
expected from the Eastern Kenai Peninsula across the Southcentral
Coast to the Canadian border through Thursday. Below normal to
much below normal temperatures make a return to mainland Alaska
including Southcentral beginning Friday of next week.

CC

&&

.AVIATION...

PANC...

Snow has come to an end overnight and should remain so through
today and VFR conditions will persist through tonight. The next
system rolls in on Sunday and is set to bring another round of
heavy snow Sunday evening through Monday morning. The bulk of the
snowfall is expected between midnight Sunday night through noon
Monday. During periods of heaviest snow, rates of an inch per hour
is likely. Temperatures are trending colder with this next system,
so, snow will be less dense compared to the most recent event.

KM

&&

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