421
FXAK68 PAFC 121329
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
529 AM AKDT Fri Jul 12 2024

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

Friday morning, a front will move into the western Gulf and
across Kodiak Island. A triple point low will then spin up along
the front near Kodiak Island. The front will continue to lift
toward the northern Gulf through Saturday as the surface low
drifts northeast along the Kenai Peninsula. These features are
tapping into abundant moisture from the Pacific with the
southeasterly steering flow ahead of the front advecting that
moisture across all of Southcentral through at least the first
half of the weekend. Given the predominantly southeasterly flow
ahead of the front, the highest precipitation amounts will be
along the coastal mountains and western Susitna Valley. For areas
in the lee of the Chugach Mountains, some rain will likely move
over these areas late Friday, as a weak wave moves ahead of the
main system and prior to the development of the strong cross-
barrier flow. Precipitation will then taper off and become lighter
and more showery for overnight Friday into early Saturday before
the trough begins to lift north and the strong downsloping flow
wanes, allowing steadier precipitation to fill back in. Once the
trough lifts north, rain should also develop over the Copper River
Basin.

Gap winds will be quite strong Friday afternoon and evening as
that initial wave moves north in tandem with a building coastal
ridge out ahead of the surface front. Winds could gust 30 to 40
mph through Turnagain Arm and across the Knik and Copper River
Valleys. Winds could gust to around 50 mph for the Anchorage and
Eagle River Hillsides.

There is better model agreement with how quickly the front and
its attendant upper-level wave move from the western Gulf to the
Northern Gulf. However, there are still some slight differences
with the timing of precipitation waning and starting up again,
especially for those locations in the lee of the Chugach. There is
some hint of a band that sets up between the northern Kenai
Peninsula, Anchorage, and Susitna Valley. Model uncertainty grows
by late Sunday into Monday. Overall, conditions look to remain
unsettled across much of Southcentral into next week as an upper
low stalls over Southwest Alaska and multiple troughs rotate
through the region.

-TM / rux

&&


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

Rounds of shortwaves moving through the Aleutian Islands and the
Southwest along the southern part of an upper level low will
bring periods of rain and clouds through most of the weekend.
Foggy conditions over the Aleutians and Pribilof Islands will
continue this morning. Additionally, strong winds funneling
through the Kamishak Bay into Bristol Bay will continue through
this afternoon.


&&


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

On the Alaska weather map, a closed upper level low over the
Yukon Delta slips Southeastward into the Northern Gulf of Alaska
by the end of the forecast period. A major shortwave trough
extends across the Bering to a second weaker low exiting the
Russian Far East near Magadan. This low continues into the Western
Aleutians by Thursday. The upper level ridge across the Eastern
Interior weakens briefly but hold it place through the week.
Forecast model confidence remains good with only the occasional
trough rotating through the pattern to temporarily upset
continuity. Heaviest rainfall starts over Southwest Alaska Monday
and spreads Eastward. The Eastern portions of Southcentral Alaska
expects heavier rains along the coasts into Southeast Alaska by
Tuesday. Heavier rains develop across Cook Inlet, over the Kenai
Peninsula into Prince William Sound and Kodiak Island through
Thursday once the low moves into the Gulf. Lesser amounts of rain
will fall over Southcentral areas away from the coasts. The
Western Bering low spreads heavier rains into the Western
Aleutians on Thursday.


 Kutz

&&.AVIATION...

PANC...VFR conditions will persist through the TAF period. A
strong Bering Sea front extending into the North Pacific will
lift northeastward towards Southcentral Alaska through this evening
and tomorrow. Gusty southeast winds will pick up again ahead of
the front this afternoon as the pressure gradient tightens, with
gusts to 35 kt possible. By late afternoon, showers are expected
over the terminal with initial push of moisture. VFR ceilings and
visibilities should remain due to southeast flow.

Later this evening, flow becomes down-inlet dominant as a triple-
point low lifts northward near Kodiak Island. By early Saturday
morning, high confidence that another push of moisture will bring
steady, light rain to the terminal.

&&


$$