Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 211155
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
355 AM AKDT Wed Oct 21 2020

.ANALYSIS AND UPPER LEVELS...

High pressure persists over the Southwest Alaska, keeping a dry
pattern across much of the mainland. A tight pressure gradient
between the upper level ridge over the eastern Bering and
Southwest Alaska and trough over the eastern Gulf is helping to
keep the outflow winds across much of the North Gulf Coast. Gusty
conditions have been observed from Seward to Valdez overnight and
are continuing this morning as cold air advection moves in over
Southcentral.

A much more active pattern is set up across the Bering and
Aleutians as two North Pacific lows enter the forecast area. The
first strong low south of Dutch Harbor is just starting to impact
the eastern Aleutians and AKPEN this morning as its front lifts
northward. The second system is farther west positioned south of
Shemya, which is also bringing strong winds and precipitation to
the western Aleutians as this low strengthens.

&&

.MODEL DISCUSSION...

Models remain in good consensus through the next few day. There is
better agreement with today`s model runs in terms of placement of
the low pressure system over the Bering Sea and timing with the
associated front moving into Southwest Alaska starting Thursday
afternoon.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2 through
Thursday night)...

Generally dry offshore flow is expected to continue over Mainland
Southcentral over the next couple of days. Gusty offshore flow
across the North Gulf Coast and Eastern Kenai Peninsula peaked
this morning and will slowly diminish through today. The
Matanuska Valley will be the exception where gusty northeast winds
will prevail through Thursday. The front heading north toward the
Western Gulf will make slow progress. This front may stall for
a while over Kodiak bringing steady rain to the island Thursday
through Thursday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Wednesday
morning through Friday afternoon)...

High pressure is retreating to the north this morning as a
frontal system approaches. Today will feature seasonable
temperatures and mostly clear skies with a few patches of clouds
mainly over the higher terrain. Wednesday afternoon winds will
increase across the AKPEN with rain chances increasing. Strong
winds and moderate to heavy rain expected across the AKPEN late
Wednesday into Thursday. Strong winds will also affect coastal
areas of the Bristol Bay region Wednesday night into Thursday.

Precipitation will then move inland across the Bristol Bay and YK
Delta region Thursday afternoon through Friday. Some snow is
possible Thursday night and Friday mainly over the Kuskokwim Delta
before changing over to rain, with little to no accumulations
expected.  Otherwise, snow will be more common over the Kilbuck
mountains late Thursday and Friday. Winds will gradually decrease
on Friday as the front weakens and the pressure gradient loosens
up.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Wednesday
morning through Friday afternoon)...

High pressure and light winds will occupy the northern Bering
Wednesday while two strong frontal systems impact the Aleutian
Chain on Wednesday. Storm force winds along the eastern system of
the two fronts are expected over the eastern Aleutians on
Wednesday, extending into the eastern Bering and Bristol Bay for
Wednesday night. The western front is associated with the
stronger of the two lows and will bring gale force winds and rain
to the western Aleutians Wednesday through Thursday. The two
fronts will then merge on Wednesday night to bring a broad region
of gale force winds and rain to the Bering on Thursday. By this
time, the two lows will have conglomerated into one near Adak,
creating a broad, strong occluded low. Cold air wrapping around
the southern flank of the low on Friday should bring another round
of gale force winds and rain from Dutch Harbor to the Pribilofs
as winds and waves slowly subside across the region.

&&

.MARINE (Days 3 through 5: Friday through Sunday)...

Gulf of Alaska:

A well developed front moves to the North Gulf Coast by Sunday.
The track and development vary considerably, but widespread
southeasterly gale force winds and waves will occur across the
Gulf through Saturday. The area of gale force winds then retreats
to the Barren Islands area Saturday, leaving small craft winds
over the Gulf slowly diminishing over the Northern Gulf through
Sunday.

Bering Sea:

A strong low and front moves into the Bering through Sunday.
Track and development of the system vary considerably, but overall
area coverage looks reasonable, with gale force winds and waves
wrapping the low as it spreads over the Bering. High end gale
winds expected in Bristol Bay near Alaska Peninsula channeled
areas for Friday. The wind-wrapped low brings a second round of
gale force winds across the Eastern Aleutians Friday and Saturday.
The entire system slowly diminishes to small craft winds through
Sunday.

&&

.LONG TERM FORECAST (Days 3 through 7: Friday through Tuesday)...

By Friday, a front associated with a large low across the Bering
Sea will have made its way inland on the southwest coast, across
the AKPEN and Kodiak Island. This will bring precipitation across
the areas, with it propagating into Southcentral Saturday and
Sunday. Gale force winds are expected with the low over the Bering
until it begins to dissipate on Saturday. The Anchorage Bowl
looks to remain relatively dry until Monday before drying out
again Tuesday. Precipitation will continue for the Bering, the
southwest, higher elevations and coastal locations through
Tuesday. Precipitation should be a wintry mix at lower elevations,
with temperatures aloft staying warm enough to not turn all
precipitation to snow. Expect snow at higher elevations through
the forecast period.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 150 155 160 165 170 172 179 180 412 414.
  Gales 130-132 136-138 171 173-178 181 185 352 411 413.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...ALH
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RC
MARINE/LONG TERM...MK/CK


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