973
FXAK68 PAFC 261334
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
534 AM AKDT Thu Sep 26 2024

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

A disorganized trough remains positioned over the Gulf of Alaska
this morning with a weak upper-level ridge trying to push into the
Copper River Basin from east. A compact low sits east of Kodiak
City and will continue to move south through the day with showers
and gusty winds for the northern and eastern portion of the island
today. Farther north along the coast, weak shortwaves moving east
along the Gulf coast and Sound will continue to produce scattered
showers for most areas today, with lower rain chances farther
inland across the lower elevations of the northern Susitna Valley
and Copper River Basin. With the cool and wet airmass in place for
many areas, areas of fog have developed this morning, with the
densest areas of fog along the Copper River Valley.

A pattern change begins to take place on Friday as a system from
Kamchatka digs into the Bering and amplifies the pattern.
Southcentral will remain downstream of this feature, with building
heights and drier weather in store for Friday, but nor before a
few areas of very light rain across Cook Inlet late Thursday night
into early Friday morning. Some sunshine is even possible as
subsidence develops behind a stretched out upper level front as it
moves northeast out of the area. Come Saturday the bering trough
will take on a negative tilt, with it`s front moving into the
western Gulf frost early Saturday and into the Kenai Peninsula and
Sound later in the day. With ridging developing to the north,
most of the precipitation will remain over Kodiak, the Sound, and
the western Kenai Peninsula south of approximately Ninilchik.
Additionally, with cooling temperatures aloft, some light snow
will be possible for elevations above 3000 ft.

-TM/CJ

&&


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

Increasingly unsettled weather is expected as a low west of Saint
Matthew Island this morning moves across the Bering Sea and
towards Bristol Bay through Sunday morning. Generally expect
sustained winds to small craft speed and rain/rain showers
associated with this low complex. Forecast confidence remains on
the lower end with exact details; models continue to struggle with
the evolution of the low complex as multiple centers develop and
phase with each other. The biggest forecast questions will center
around: (1) the potential for isolated marine thunderstorms due to
colder air and robust vorticity embedded within the low complex,
and (2) precipitation amounts associated with a front moving into
the Alaska Peninsula, Kuskokwim Delta, and Bristol Bay from Friday
into Saturday.

&&


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

A broad longwave upper level trough stretches from the Russian
Far East to the Canadian Provinces, with several energetic
shortwaves passing through the flow. A closed low center in the
Southeast Bering tracks over the Alaska Peninsula and Northern
Gulf before dissipating around the Copper River Delta. The GFS /
ECMWF / CMC deterministic blends handle the systems quite well
through most of the forecast period, becoming less confident by
midweek. This drop in confidence is due to the possible influence
of North Pacific lows through Wednesday. Heaviest precipitation
spreads from the Pacific side of the AKPEN, Western Cook Inlet to
the slopes of the Alaska Range and Kodiak Island on Sunday to the
Eastern Kenai Peninsula and Prince William Sound for Monday, and
diminishing Tuesday. Locally moderate rainfall is expected over
the Aleutians, AKPEN, and lesser amounts further inland across
Southcentral Alaska. A new front enters the Western Aleutians on
Monday and sweeps to the Central Aleutians and Bering for
Wednesday. Gusty outflow winds are expected as the Bering low
moves across the Gulf, with gale force winds expected in the
offshore waters, diminishing by Tuesday.

&&

.AVIATION...

PANC...IFR cloud ceilings are expected early this morning with a
chance for development of vicinity fog. Fog may roll over onto the
terminal should calm winds prevail; however, the light northerly
flow as of 4 AM may keep slightly drier air in place near the
surface and prevent fog from advecting over the terminal.
Conditions should improve to VFR around 10AM. Periods of light
rain showers possible through today.

&&


$$