918
FXAK68 PAFC 050024
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
424 PM AKDT Fri Oct 4 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Sunday night)...

The pattern over Alaska is currently dominated by very large
vertically stacked low centered just south of Nunivak Island in
the eastern Bering Sea. An occluded front continues to push
through the northern Gulf late this afternoon with a band of rain
and gale-force winds. Widespread showers across the Prince William
Sound and the eastern Kenai Peninsula will give way to steady
rain moving in from the south. Southeasterly gap winds are peaking
through this evening as the front makes its way northward.

As the main upper trough axis becomes more negatively tilted
early tonight, the frontal orientation in the Gulf will turn more
west to east as it pushes onshore along the north Gulf coast. This
will assist in slowing down the front, bringing a prolonged
period of prefrontal rain, enhanced by upslope flow, for the
eastern Kenai Peninsula and portions of the Prince William Sound.
Total rainfall amounts between 2 to 6 inches are expected in
coastal mountains of the southeastern Kenai Peninsula and western
Prince William Sound. Strong southeasterly downsloping flow will
keep the remainder of Southcentral dry. As the front moves onshore
and spreads inland tonight through early Saturday, there will be
a better chance of a brief period of sprinkles or light rain
inland.

For this weekend, the Bering Sea low will weaken and transition
eastward to the Gulf, while a series of short-waves rotate around
the very large cyclonic flow around the low center. Cold air aloft
will lead to an unstable airmass, giving a showery characteristic
to precipitation, with locally heavy rainfall. Persistent south
to southeast flow will provide for continued wet conditions along
the coast. Inland areas will be drier, but will likely see a few
showers as short-waves track inland. Skies will be mostly cloudy,
though there could be an occasional break of sun over the
Southcentral interior.

-ME/SEB

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, AND THE BERING
SEA/ALEUTIANS (FRIDAY NIGHT to SUNDAY NIGHT)...

The Bering Sea low pressure system that has dominated for the
last few days continues to bring strong winds and light to
moderate rain to locations across the region. The center of the
low is now located northeast of the Pribilof Islands and has begun
to fill, raising from 951 mb to 960 mb over the last 22 hours.
High Wind Warnings remain in effect until 8 pm this evening for
the Pribilof Islands and Eastern Aleutians, where gusts to 75 mph
are possible. Wave heights in marine zones north of the Aleutian
islands will continue to die down through the weekend. This low
should take a southeasterly track through Bristol Bay on Saturday
and cross the Alaska Peninsula into the western Gulf by Sunday
morning.

A shortwave trough on the backside of the low is currently
swinging down from the eastern Bering. This will bring a quick
shot of higher winds and precipitation to the western and central
Aleutians late tonight and into tomorrow morning. Looking ahead
to Sunday, much of western Alaska will be under broad cyclonic
flow following the departure of the low into the Gulf. Starting
Sunday night, there is model agreement for some weak ridging to
begin pushing into the eastern Bering.

-TK

&&

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

The long term period begins with the storm system in the Gulf
continuing to wind down. The stalled low will continue to weaken
and spin in the Gulf keeping unsettled weather and a slight chance
for showers to remain for the northern Gulf coast through
Tuesday. The upper level trough over mainland Alaska and the Gulf
becomes more negatively tilted and less defined into Thursday as
it begins to interact and merge with an upstream system in the
Bering, forming a broad longwave trough spanning from Eastern
Siberia to Canada.

Upper level ridging over southwest Alaska and the Aleutians on
Tuesday will give way to fairly zonal upper level flow as well as
a surface low that will brush by the western Aleutians through
Wednesday. This fast moving system has the potential to bring
briefly unsettled weather to the western and central Aleutians
Tuesday into Wednesday, out ahead of a more potent system emerging
off of the Kamchatka Peninsula. The second system will enter the
western Bering by Thursday before crossing the Aleutian chain and
strengthening by Friday morning. This system has the potential to
become another impactful storm given sufficient upper level jet
support and access to ample moisture, bringing possible heavy rain
and gusty winds for the eastern Aleutians and AKPen by the end of
the period.

-JH

&&

.AVIATION...

PANC...West to northwest winds will continue this afternoon before
a return to southeasterly winds make a returns this evening
with winds gusting as high as 25 to 30 kts. Later tonight, around
10Z, a front passing over the terminal makes light rain showers
and ceilings below 5000 ft more likely, for an hour or two, as
winds diminish somewhat. Winds restrengthen after the passage of
the front and ceilings lift for Saturday morning.

&&

$$