718
FXAK68 PAFC 191316
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 AM AKDT Sat Oct 19 2024

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

The pattern we`ve seen in place now for the past couple days
remains in place this morning as stout northerly flow between a
strong upper ridge over the Bering Sea and western Mainland and a
trough over the eastern Gulf continues to fuel gap winds through
several of the favored spots for channeled flow along the Gulf
coast. An impressive dust plume stemming from the Copper River
Delta now extends all the way south to Middleton Island and is
becoming wrapped up in a mesoscale low spinning near Kayak Island.
This dust is originating from silt along the Copper River kicked
up by a narrow jet of strong winds shooting out of the the river
valley into the northern Gulf. Dust has also been kicked up
intermittently across parts of the Mat Valley near Palmer, where
strong winds gusting near 60 mph at times overnight are finally
beginning to subside. Otherwise, almost perfectly clear skies are
in place across all of Southcentral as a cool and very dry air
mass continues to stream south.

Little change to the pattern is expected today, with mostly clear
skies and gap winds near the coast and out towards the Barren
Islands expected to persist through this evening. By tonight into
Sunday, a pattern shift will begin to take shape as the upper
ridge out west shifts east and begins to encroach farther into
Southcentral. This should finally mark an end to the persistent
gap winds as cold advection ceases and as prevailing flow becomes
more westerly with time through Sunday night.

By Monday, a bigger change in the pattern will begin to take shape
as a potent storm system moves from northeast Russia into the
Chukchi Sea. A trailing front associated with this low will
approach Southcentral from the west by Monday evening as a fast
moving shortwave also moves quickly from Southwest into
Southcentral by Monday night. Strong warm advection and
southwesterly flow will warm low level temperatures substantially
before precipitation with this system arrives. This will likely
be enough to make this mostly a rain event for elevations below
roughly 2,000 ft for most of Southcentral as light to moderate
precipitation overspreads much of the area from west to east on
Monday night. Several inches of snowfall will be possible at
higher elevations across the various mountain ranges on Monday
night, particularly for parts of the Chugach Range and Talkeetnas.

-AS

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Days 1 through 3: Today through Monday)...

A mid-level front continues to make its way across the eastern
Bering this morning and is now approaching Nunivak Island and the
Kuskokwim Delta coast. Despite the presence of the front,
precipitation should be relatively light and isolated. Most areas
will see limited precipitation with the front`s passage and
instead experience increased cloud cover. A cool air mass ahead
and behind the front is keeping temperatures below freezing across
all of Southwest Alaska. High temperatures are expected to only
warm into the mid to upper 30s this afternoon, with a gradual
warming trend into the 40s Sunday and Monday, as warm air
advection arrives with the incoming front. For today, occasional
light snow will be possible over the Kuskokwim Delta and western
portions of the Lower Kuskokwim Valley. Accumulations should be
minimal.

Attention then turns to Saturday night and Sunday as a deepening
Kamchatka low pushes a much stronger front into the Bering. An
expanding wind field of gales are forecast to spread across the
western Bering later this evening into Sunday, eventually reaching
the west coast of Alaska by midday Sunday. Within the swath of
gales, a belt of storm force winds will also extend from west of
Saint Matthew Island down into the Western Aleutians during the
morning hours on Sunday.

As has been advertised in previous forecasts, the stage will be
set for an extended period of southwesterly flow into the west
half of the state. Gales reach the Kuskokwim Delta Sunday
afternoon and then the Bristol Bay coast by Sunday night. Models
have been in good agreement with keeping strong onshore flow
through at least Tuesday of next week. This will result in
elevated water levels with potential coastal erosion and flooding
coincident with high tides on both Monday morning and Tuesday
morning. A coastal flood warning remains in effect for the
Kuskokwim Delta coast. A coastal flood watch is in effect for the
Bristol Bay coast.

-BL

&&


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

The Alaska Weather Map starts off with a closed upper low over
the Central Chukchi Sea that slips into the Canadian Arctic
through the forecast period. Its associated trough bisects the
Bering and moves rapidly into Western Alaska for Wednesday. This
long fetch system brings widespread gusty winds and moisture into
the Mainland through the week. A group composite of GFS / ECMWF /
UKMET and Canadian models carry the system through midweek, with
growing uncertainty towards Friday. The gradient is expected to
relax over the Mainland, but remains quite organized across the
Aleutians and Bering.

The surface weather map brings in a strong front that moves into
Western Alaska Tuesday, and continuing inland through the week.
Widespread windy conditions with gale force gusts and locally
heavy rain marches into Western Alaska. Areas of potential coastal
flooding are expected to spread as far South as Cape Newenham.
Areas of gale force winds continues across the Central to Northern
Bering around St Lawrence and St Matthew Islands diminishing
Wednesday. This system continues spreads areas of heavy rain,
which with freezing precipitation or heavy snow developing further
inland. Gusty winds with gale force gusts move over the Central
and Eastern Aleutians late in the period. The downwind leeside
precipitation shield reduces but does not diminish the chances of
rain or rain and snow mixed across Southcentral Alaska through
midweek. A surface low developing on the front in the Gulf on
Wednesday increases the chance for rain or rain-snow mixed to
spread across Southcentral Alaska through Thursday.

&&


.AVIATION...

PANC...VFR conditions will persist. Northerly winds of 10 to 15
kts will slowly weaken throughout the morning, dropping to around
6 kts and remaining there through the rest of the TAF period.

&&


$$