Gale Warning 696, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKDT Tue Oct 8 2024

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

The upper level pattern is beginning to shift, under the
influence of a zonal jet stream south of the Aleutians. The upper
low over much of the state and Gulf of Alaska is much less
organized today as all three low centers are weakening.
Southcentral Alaska is left between disturbances with only
lingering mid/high level clouds over the area. The major players
in the forecast coming up the next few days are a weak disturbance
approaching Nunivak Island and a much stronger shortwave in the
western Bering Sea.

Synoptically the setup remains much the same with seasonally warm
sea surface temperatures and cold air aloft ahead of a weak
trough. The major difference in model guidance today, as the
trough sharpens in response to building heights over the eastern
Bering Sea, the wave energy is consolidating in the western Gulf
of Alaska, with hints of closing off. The potential rain/snow
setup remains unchanged with a period of precipitation late
Wednesday evening into Thursday morning. Guidance is not in great
agreement with placement of precipitation, however, forecast
thinking has not changed as far as expecting precipitation between
Seward and Palmer. The next challenge is precipitation type. The
air mass in the low levels is not that cold, nor is there much
cold advection to speak of. However, with convective precipitation
there should be some dragging of cold air from aloft toward the
surface along with wet-bulbing and dynamic cooling. All that to
say snow levels should be in the 500-1000ft range, with a mix
making it to the surface. At this point, accumulations look to be
mainly confined to higher elevations and up to a couple inches.

That system pushes out pretty quickly on Thursday as the next one
takes shape. A strong developing low at the triple point
approaches Kodiak Island on Friday. Strong winds and waves are
expected with this system, with winds approaching hurricane-force.
Stay tuned to the forecast for additional information.

MTL

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (TONIGHT THROUGH FRIDAY NIGHT)...

The shortwave trough that flattened out our weak Bering ridge
today continues to take its energy eastward into Southwest Alaska.
The front associated with it will make landfall this afternoon,
bringing possible precipitation to the Kuskokwim Delta and
northern Bristol Bay region. This should come in the form of rain
for coastal areas of the Kuskokwim Delta. However, with cold
temperatures in place from recent cold air advection, locations
in Bristol Bay and more interior Kuskokwim Delta could see some snow
or a snow/rain mix. All precipitation will be short lived as this
system quickly fizzles out by Wednesday mid-day.

During this same time frame, the western Aleutians and western
Bering will begin to feel the first signs of the powerful low
pressure system developing in the Bering. By Wednesday these areas
will see 35-45 mph winds and seas to 15 ft. The low center will
continue to deepen and slide east to just southwest of the
Pribilof Islands by Thursday mid-day. At this point the main core
of strong winds will be situated on the backside of the low,
hitting the western and central Aleutians with strong gale force
winds. From here, the low looks to dive southeast Thursday night
and bobble on the south side of the eastern Aleutians and Alaska
Peninsula for the remainder of our outlook while strengthening.
Gusts from 50-75 mph are possible for Bristol Bay, the eastern
Aleutians and the Alaska Peninsula by Friday morning.

A primary concern is the prolonged duration of gale to storm
force northerly winds the eastern Aleutians are set to receive
starting on Friday. An extremely large fetch that includes much of
the Bering Sea could result in seas up to 30 ft in marine zones
and up to 25 ft in Unalaska Bay. Additionally, these winds will
hold steady from Friday afternoon through Sunday.

TK

&&

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

A large storm-force low centered south of the Alaska Peninsula on
Saturday will dominate the weather pattern across southern Alaska
through next week. The large low will have a broad wind field,
with a storm force front (and potential hurricane-force gusts)
lifting across the north Gulf coast on Saturday while cold,
Arctic air streaming south across the Bering Sea leads to a large
area of gale and storm force winds blowing across the Pribilofs,
central and eastern Aleutians, and Alaska Peninsula. While the
front in the Gulf lifts quickly north and weakens rapidly as it
pushes inland over Southcentral Alaska, gusty winds in the Bering
Sea will diminish much more slowly as Arctic air continues to
surge southward through Monday. High seas can be anticipated in
association with this low, likely up to 25 feet particularly in
the area between the Pribilof Islands and the eastern Aleutians
for much of the day Saturday and along the front in the Gulf
Saturday morning before it moves inland.

A band of precipitation also lifts across southern mainland
Alaska on Saturday along with the front, primarily falling as rain
as the low draws warm, moist air up from the subtropical Pacific.
The heaviest rain falls along the coastline, focusing along the
eastern Kenai Peninsula, especially on Saturday. After the front
lifts into the Interior, precipitation will mainly focus along the
coast of the Gulf of Alaska and the north side of the Alaska
Peninsula and eastern Aleutians in the form of upslope shower
activity. Arctic air streaming southward will contribute to
unstable conditions that also produce bands of showers across the
eastern Bering Sea through Monday.

Along the far western portions of the domain, the extratropical
remnants of what is currently Tropical Depression 21W in the
western Pacific have the potential to bring gale force winds
through the western Aleutians beginning Sunday. This low tracks
south of the Aleutians, bringing a band of light to moderate rain
as far as the eastern Aleutians by Tuesday, though winds likely
weaken below gale force east of Kiska. This low has some
potential (low, <30% chance) to strengthen as it tracks toward
the Gulf of Alaska later in the week.

Quesada

&&

.AVIATION...

PANC...VFR conditions and light winds will persist. A thin cloud
deck just below the 5000 ft threshold has recently been drifting
over and near the terminal this afternoon, and it's a bit unclear
how long this could stick around this evening. However, lowering
of ceilings to MVFR range or lower does not appear likely.

&&