Gale Warning 574, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
528 AM AKDT Thu Sep 12 2024

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

A negatively tilted trough with multiple upper level shortwaves
is currently in place from the Norton Sound to the central Gulf.
The main feature of note is a ~986 mb low currently 50 nm east of
the Barren Island. Gales are wrapped in an arc around the low from
Kayak Island towards Seward and then to the tip of the Kenai
Peninsula. The low will slowly occlude and track into the eastern
Gulf through Saturday.

Fairly widespread rain is expected once again today and will
slowly dissipate from west to east through Saturday. Two upper
level features, the main upper low associated with the Gulf low,
and another closed upper level low/vorticity maxima, are
responsible for the rain. As the Gulf low moves east, the other
vorticity max will move over the Kenai Peninsula. This will create
another area of lift overnight, bringing a band of rain that
looks to set up over Anchorage and the western Kenai Peninsula.
Both disturbances will move east on Saturday, which will keep the
Copper Valley and higher terrain a little on the rainy side, but
otherwise a shortwave ridge will build in from the west Friday
afternoon through midday Saturday. Some sun is possible for the
Cook Inlet areas Friday afternoon, though fog and low stratus may
redevelop on Saturday morning. The drier weather will be short-
lived as a front from a broad Bering low pushes into Southcentral
on Saturday. This will drive up the gap winds as a coastal ridge
builds in addition to more widespread rain.

-Jones

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS
(Days 1 through 3: This afternoon through Saturday evening)...

Currently across the Bering Sea there are several systems that
are either weak, weakening, or moving out of the area. Firstly
over Southwest Alaska, an exiting trough continues to pull some
diminishing gusty winds across the Alaska Peninsula. Rainfall in
the area has largely moved out and the region will likely see a
reprieve in rain until some low chances arrive Friday afternoon.
Some areas of fog are possible in the Alaska Peninsula, near King
Salmon, this morning as the trough continues to exit, but will
likely lift into the later morning. Over the Eastern
Bering/Aleutians, a weak ridge is in place allowing for more muted
conditions, however areas of fog persist throughout this region.
Behind the ridge, over the western/central of the Bering, a front
is pushing across, bringing a brief round of rain showers to
areas of the Aleutians as it passes. The front is pushing the
ridge along, and given the weak/deteriorating structure of both of
these features, a general unsettled pattern is expected across
the Central Bering. By the time the front pushes over the Pribilof
Islands Thursday afternoon, rainfall will be light. The remnants
of the front will continue to advance eastward, moving over
mainland Southwest Alaska by Friday morning.

Attention then shifts to the Bering for Friday and Southwest for
Saturday as a much more organized storm system, with potentially
strong winds and deep moisture fetch, looks to gather and
approach the region. A digging trough across eastern Russia will
drop southward into the Bering Sea with multiple shortwaves
rounding the base of the trough across the Aleutians for Friday.
At the surface, this will be seen as a surge of wind and rain from
the southwest moving over the Central Aleutians near Adak Island
late Friday morning. Expect showery conditions across the Western
Aleutians with more in the way of steady rain across the Central
Aleutians most of Friday into Saturday. As the pattern amplifies
and the trough continues to dig southward now into the North
Pacific, cyclogenesis looks to take place across the central
Bering west of the Pribilof Islands Friday night. There are still
some questions and uncertainties regarding the evolution of this
"to be" gale- force low. The track of this surface low is still
facing much discrepancies between the model solutions. Trends in
guidance have had the low pulling northward towards the Bering
Strait by Saturday morning/afternoon. This track would lead to
a favorable set-up for onshore winds and steady rainfall across
Southwest Alaska. Stay tuned as details on this system continue
to be ironed out.

-CL

&&

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

Models are pointing towards a trough moving across Southwest
Alaska into Southcentral and Gulf region over the weekend. Strong
south to southwesterly onshore winds across the southwestern coast
of the state along could allow for minor coastal flooding and
high seas across the Kuskokwim Delta and low-lying coastal
communities through late Sunday into early Monday. Full moon is
expected Tuesday, which could influence higher tide levels around
this timeframe as well. As the low moves east out of Southwest
Alaska, its center will more likely stay north of the Alaska
Range. There are some differences with the characteristics of the
low and especially with the front, but rainfall is highly likely
this weekend with decreasing coverage later Sunday into the early
week ahead. A ridge looks to build behind the low. There is low
confidence with how strong and how long that ridge will be
around, because not far behind, another system is looking to occur
Monday and Tuesday from the Bering Sea and Aleutians. At this
time, a developing North Pacific trough and a Kamchatka low may
converge in the southern Bering Sea near the central Aleutians by
Tuesday morning. Depending on how it develops and tracks in time,
west to northwesterly winds could be gusty through bays and
passes in the eastern Aleutians and Alaska Peninsula with a low to
medium potential of reaching storm force Tuesday morning for the
eastern Aleutians somewhere around Seguam Island and Alaska
Peninsula near False Pass to Shumagin Islands. Because of model
differences, the swath of storm force winds could end up a little
more north toward the Pribilof Islands should the track of the low
be more north. This latter scenario is suggested in the Canadian
model and is more of an outlier. This system will continue onto
Southwest Alaska sometime Tuesday afternoon and into Southcentral
by Wednesday.

rux

&&

.AVIATION...

PANC...A brief period of VFR conditions are expected this morning
as downsloping produces some drying in the lower levels. However,
fog and low stratus are present in the Inlet and north of the
terminal, so periods of MVFR to IFR conditions are possible should
that move over the terminal. A wind shift in the midlevels to the
northwest will end downsloping this afternoon, which will likely
produce MVFR ceilings again as more light rain moves into the
area.

&&