Gale Warning 640, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
549 AM AKDT Sun Sep 29 2024

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

Key Messages:

- A storm force low moves into the Gulf of Alaska offshore waters
Monday, bringing Storm Force winds with potential for Hurricane
Force wind gusts and wave heights of 30 feet or higher Monday into
Tuesday morning.

- Models continue to converge on the track of Monday's low, which
has trended further south and east in the latest model runs. Thus,
the strongest winds and highest waves will remain well offshore,
with most coastal areas maxing out at 25 to 40 kt winds and 8 to 15
ft seas.

Discussion:

Scattered showers remain ongoing this morning over the southern
Kenai Peninsula, Kodiak Island, and the northern Gulf as a quasi-
stationary front lingers over the area. The front and associated
trough will weaken and wash out later today with most of the showers
gradually winding down. Temperatures today look similar to yesterday
with most inland areas of Southcentral reaching the upper 40s to mid
50s. Should see some more breaks in the cloud cover today,
especially over the Copper Basin where drier air will help to erode
cloud cover more quickly. Mid and higher level clouds will start to
build back in over Kodiak Island and the Kenai Peninsula later today
as the cloud cover from the North Pacific low spreads into the
western Gulf.

Speaking of the North Pacific low... Early morning satellite imagery
shows that it is quickly lifting northwards towards the southern
Gulf. An expansive cloud shield already accompanies this system as
it starts to deepen. Deterministic models and ensemble data has
previously struggled with the track of this system, but have started
to converge on a solution. The last few model runs have shifted the
track to the south and east, and the NAM has come around to joining
the other models in the track of the low. However, they are still
struggling on on the strength of the low...generally bouncing
between 940 to 970 mb, but starting to trend towards a slightly
weaker low pressure center. Regardless, even a 970 mb low is quite
strong and will result in storm force winds with gusts to hurricane
force over the offshore Gulf zones. In addition, significant seas
still have the potential to build to above 30 feet Monday into
Tuesday. This shift in track to the south and east will alleviate
some of the concern for high winds over Kodiak Island, but there
could still be a period where northerly winds of 40-55 mph will be
felt Monday through early Tuesday. This low will rapidly track
eastwards towards Southeast Alaska by Tuesday afternoon/evening.

For inland areas of Southcentral, the track of the Gulf low will
place much of it in off-shore flow resulting in drier conditions and
less cloud cover as drier air is pulled southwards.

- PP

&&

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

An occluded gale force low is centered in the eastern Bering Sea,
while an elongated, negatively-tilted trough remains strung out
over Southwest Alaska this morning. A band of rain showers
continues to extend across Bristol Bay into the Kuskokwim Valley
near Aniak in association with a weakening, quasi-stationary
front. The front wobbled back west overnight in response to a weak
shortwave trough lifting across Kodiak Island, but will resume
its slow eastward progression today as the influence of the
eastern Bering low becomes stronger due to its increasing
proximity. This should push rain showers into Iliamna and the
Middle Kuskokwim Valley through the day. Tonight, the front
begins to fracture and precipitation will trend lighter.

The low in the eastern Bering Sea will weaken today as its center
tracks along the southern Alaska Peninsula. The main impacts from
this low will be rain showers and winds below gale force. Across
the Bering Sea/Aleutians, generally expect isolated to scattered
showers as cold air sinks southward behind (to the west of) the
low. Tonight, an intensifying low pressure system entering the
Gulf of Alaska will begin to shift winds out of the east across
Southwest Alaska and the eastern Bering Sea. This will push the
weakening front over inland Southwest Alaska back westward and
renew rainfall activity briefly. Light rainfall pushes westward
with the front to Dillingham and the Ahklun Mountains by Monday
afternoon before dissipating. Dry offshore flow begins to
dominate, with a ridge pushing in aloft from the Bering, which
will keep Southwest Alaska precipitation-free Monday night into
Tuesday.

Out west, a large but fairly weak low tracks into the western
Bering Sea late tonight. Southerly winds, with a small pocket of
gale force winds sweep to the eastern Aleutians through Monday
night, accompanied by a band of rainfall. The low weakens below
gale-force as it pushes across the Alaska Peninsula and into the
North Pacific on Tuesday. A second broad and weak low tracks into
the Bering Sea from the west on Tuesday as well, likely bringing
winds below gale force and another round of light rain. Heading
into mid-week, there is potential for a stronger low to develop
off Kamchatka and bring more unsettled weather to the Bering Sea.

Quesada

&&

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

The Alaska Weather map continues with a progressive pattern into
the weekend. An upper level low center South of the Alaska
Peninsula weakens as it drifts across the Gulf of Alaska towards
Queen Victoria Island dissipating by Friday. Locally moderate rain
and gusty winds accompany this surface low over the AKPEN and
Kodiak Island, diminishing from North to South as the low moves
East to Southeast. Over the Canadian Provinces, a blocking ridge
sets up through the week. ECMWF and GFS have handling the larger
scale features well, but uncertainty increases with local weather.
A strongly developing low exiting the Russian Far East becomes a
major weather producer in the Western Bering Thursday. Periods of
heavy rain and gusty winds increasing to gale force extend over
the Western Aleutians and Bering for Thursday. Friday brings areas
of heavy rain and more gales spreading into the Central and
Eastern Aleutians and Bering, with areas of storm force gusts
swinging into the Western Bering behind the low. Heavy rains moves
over Southwest Alaska through Saturday. Areal wind coverage
decreases somewhat, with higher end gales and local storm force
lingering over the Western and Central Aleutians and Bering into
the weekend.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist. Winds are
expected to flip around to southerly again this afternoon,
sustained winds will be 10 kts or less with gusts to 20 kts.

&&