Gale Warning 315, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 AM AKDT Fri Mar 29 2024

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

An active weather pattern continues over Southcentral with the
first of two storms moving into the northern Gulf of Alaska this
morning. A front wrapping around a strong low in the Eastern
Bering Sea continues to move north into the Northwest Gulf of
Alaska where a weak low is now forming and will continue to push
north and east through Cook Inlet today. Snow levels will rise
ahead of the front resulting in a quick period of rain/snow
showers changing to all rain for the coastal areas. High mountain
locations will remain all snow. Inland areas will see a mix of
rain and snow with minimal snow accumulations. Gusty southeast
winds will develop ahead of the front with locations such a the
Anchorage Hillside, Thompson Pass and Turnagain Arm reaching wind
speeds of 35 to 50 mph later this morning. Winds in the Anchorage
Bowl will range from 25 to 35 mph with gusts to 55 mph today and
into Friday night.

A much stronger storm will move through Southcentral Saturday and
Sunday bringing rain, snow and strong winds. Models continue to
converge on a track that will bring a strong low north through
Cook Inlet on Saturday, with its its front stretching northward to
Prince William Sound. Southeasterly to southerly winds will
continue to bring moisture to coastal areas from Kodiak Island to
Cordova resulting in rain and snow Saturday and Sunday. Snow
levels will range from 800 to 1000 feet creating mostly rain at
coastal areas with snow at higher elevations. Passes and mountains
should remain as all snow during this event. This second storm
will bring another round of strong winds with sustained winds
ranging from 50 to 60 mph with gusts to 75 mph possible along the
Anchorage Hillside, and Turnagain Arm with and wind gusts 50 to
60 mph in the Anchorage Bowl. Strongest winds are expected
Saturday morning. A High Wind Watch has been issued for these
ares. Winds gusting to 45 mph are possible Saturday in the Mat-Su.

Colder air will push rapidly north and east on very strong south
to southwest winds into the Western Kenai, the Anchorage Bowl,
the Mat-Su and Susitna Valleys with snow accumulations likely at
sea level Saturday evening into Sunday on the back side of the low.
Cold and moist southwest flow will bring significant upslope
snowfall to the front range of the Chugach, the Talkeetna
Mountains as well as the Susitna Valley. Heavy snow and blowing
snow is expected in Thompson Pass Saturday and Sunday with 1 to 2
feet of snow expected as well as wind gusts in excess of 50 mph. A
Winter Weather Advisory has been issued for this area.

-CC

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, the BERING SEA and the
ALEUTIANS (Days 1 through 3: Friday through Monday)...

A broad upper-level longwave trough remains parked over the
Bering, with its axis stretching from the northwest Alaska coast
south across the central Aleutians. This longwave trough is
dominated by two upper-level lows. The first is lifting from the
base of the trough to the Y-K Delta coast this morning while the
second dives southeast from eastern Russia, replacing its
predecessor at the base of the trough by Saturday morning.

The first upper-level low will continue to track northeast as its
attendant surface low moves inland. Snow and blowing along the
coast and over the Pribilof Islands overnight will wind down this
morning as the low weakens. A developing southwesterly onshore
flow in the wake of the low, however, will allow snow showers to
develop across much of Southwest Alaska with additional minor
accumulations likely.

Snow showers will continue across interior Southwest Alaska into
Saturday morning as a secondary upper-level shortwave lifts north
following the low. Snow showers will then slowly taper off, mainly
confined to upslope mountainous terrain.

Any reprieve, however, will be short-lived as the digging upper-
level low from eastern Russia moves to the central Aleutians. The
result will be a reamplification of the long wave pattern,
allowing for a shortwave and associated surface low over the
North Pacific to strengthen and lift north toward the Alaska
Peninsula. These features will have great jet support to allow for
further strengthening as both reach southern Kodiak Island
Saturday morning. Strong winds will wrap around the surface low,
especially along the backside of the low where colder, more
unstable air will work in. Copious moisture will also accompany
this system, with widespread snow likely for much of Southwest
Alaska. The biggest challenge will be the exact track of the low,
specifically which side of the Alaska Range the center of
circulation will take. A more western track would help bring
southeasterly gap winds to places from King Salmon to Iliamna.
Any increase in southerly winds could allow for enough warm air
for a rain/snow mix in typical warmer and windier locations. An
easterly track would likely allow for mainly all snow for all of
Southwest Alaska. Whatever the track, many communities will see
several inches of new snow Saturday into Sunday along with very
strong winds both ahead of and in the wake of the low.

Over the Bering, the east Russia upper-level low will sweep a
surface trough north to south across the Bering. This trough will
usher in colder air and snow showers from west of the Pribilofs
south to the central Aleutians for Saturday. Yet another upper-
level trough and surface cold front then drop out of Siberia
reaching the Southwest coast by late Sunday. These features will
bring much colder air across the eastern half of the Bering and
western half of the state by Monday.

-TM

&&

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

A deep upper level trough over the Eastern Bering extends from
the Arctic to the North Pacific drives across the state of Alaska
through Wednesday. While the confidence of movement of the trough
is good, a number of shortwaves traveling through the pattern
increase the uncertainty in the associated weather, particularly
across Southern Alaska as several North Pacific systems add to the
mix. Deep cloudiness and periods of snow moves across the
Interior Sunday and Monday, diminishing Tuesday. Over the
Southcentral areas, the first well developed surface low marches
onshore near the Canadian Border late Monday, with gusty winds and
mostly rain spreading inland and Westward towards Prince William
Sound. Gusty outflow winds with areas of gale force winds blows
across Kamishak Bay and the Barren Islands and around Sitkinak
late Monday, diminishing Tuesday. A weak upper ridge moves into
the Interior for Thursday.

Another somewhat deep trough moves into the Bering Wednesday.
Most of the energy is deflected over the Southern Aleutians and
Bering. A developing North Pacific surface low pushes its way
across the Western Aleutians on its way just North of the
Pribilofs by Thursday. Gusty winds move over the Aleutians while
areas of gales surround the low in the Western Bering, all
diminishing Thursday. Locally heavy rainfall accompany the front
as it moves Eastward into the Pribilofs, Alaska Peninsula and
Southwest Alaska by Thursday. Another round of locally heavy rain
comes into the Western Aleutians for Thursday.

Kutz

&&

.AVIATION...

PANC...VFR conditions thru tonight. Light and variable winds will
transition to gusty and southeasterly this afternoon with the
first of two low pressure systems, the second and stronger low
not arriving until the latter half of Saturday. Any precipitation
on Friday should be light, with the best shot of a rain/snow mix
from noon thru the evening hours, and perhaps a better chance for
precip Saturday morning.

-BL

&&