Gale Warning 543, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
443 PM AKDT Fri Sep 30 2022

.ANALYSIS AND UPPER LEVELS...

The Hurricane force low that is the remnants of typhoon Kulap is
moving east across the western Bering as it weakens. There are no
observations near the low so it is hard to gauge if there are
still sustained Hurricane force winds. A weakening front is moving
across the eastern Bering and AKPen with enhanced winds and a few
showers. Across Southwest Alaska it is fairly quiet with some
areas of low stratus. A weakening low continues to move south of
Kodiak Island and will move into the Gulf. A shortwave is moving
north across the eastern Gulf supporting a surface low which will
bring rain to eastern Prince William Sound and the Copper River
Basin. Weak shortwaves are rotating into Southcentral from the
Gulf producing scattered showers across the area. Winds are light
across all of the southern mainland.

&&

.MODEL DISCUSSION...

Models are in good agreement with the weakening Hurricane force
low moving across the Bering through Saturday. However, there is
still some uncertainty on the exact track on Sunday, but most of
the models have trended north towards the Kuskokwim Delta area
where the low will make landfall albeit significantly weaker with
models showing winds 25 to 35 knots as it approaches land. The
biggest forecast challenge will be possible minor coastal flooding
or high surf along the Kuskokwim Bay area on Sunday. On Monday
another Gale force low moves across the southern Bering, however
there is some uncertainty on the track. If it tracks north this
could continue to bring high surf across the Kuskokwim Bay area.

&&

.AVIATION...
PANC...VFR conditions expected through period there is a small
chance that patchy fog and IFR or lower ceilings may develop by
Saturday morning, but confidence is low that this will occur as
weak northerly flow develops overnight which tends to bring drier
air into the area. Otherwise the Turnagain winds are expected to
continue through late afternoon or early evening with occasional
gusts to 20 mph possible before becoming light out of the north
tonight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Monday afternoon)...

An area of low pressure currently positioned in the eastern Gulf
will track northward tonight across the Alaska-Yukon Territory.
Moisture ahead of this system is pushing westward with rain
showers over Prince William Sound (PWS) and then continuing
overnight over the Copper River Basin. Meanwhile, a trough with an
embedded upper low is slowly lifting into the Alaska Panhandle in
response a transient ridge moving overhead. The combination of
the building ridge and exiting trough will cause gusty, northerly
winds to develop tonight through early Saturday for Resurrection
Bay, Passage Canal, and western PWS. After a brief break of drier
weather, a deep trough evolves into a closed upper low over the
Bering Sea. The leading front ahead of the low brings a return of
cool, cloudy, and rainy conditions over Kodiak Island and then
northward into Southcentral on Saturday afternoon/evening. A
series of upper level waves embedded in the southwesterly flow
will keep unsettled conditions through Sunday. Another trough and
upper low sets up again over the Bering Sea with a rinse and
repeat for early next week.

&&

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

At the onset of the forecast period, expect cool and mild
conditions across Southwest Alaska. Pockets of low stratus and fog
will be possible tonight. A former typhoon has undergone its
extratropical transition and is moving across the Bering. The
first wave of precipitation from this feature will reach the coast
and Bristol Bay Saturday morning, then gradually push inland. This
system will be well past its peak by the time it reaches
Southwest Alaska this weekend but it will bring wet conditions.
Southerly winds will impact the coast and the Y-K Delta but gusts
are not expected to exceed 25 mph. Late Sunday/Monday the low
will move inland. Precipitation amounts will vary across SW AK
from .75 to .10 of an inch with this system. Given the
progressive nature of the pattern (the past month) there is
already a new low churning on the horizon over the Bering north of
Adak. This low won't impact SW AK this forecast period but its
worth noting.

&&

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

The extratropical remnants of former Typhoon Kulap are barreling
across the Bering Sea this afternoon. Hurricane force winds were
detected earlier today at Shemya and north of Attu Island (on
ASCAT/Advanced Scatterometer data). The pressure gradient field
encompasses the entire Bering Sea with an estimated surface low of
956 mb. Enhanced seas with waves over 30 feet will continue
tonight and Saturday. The tight pressure gradient will continue
into Sunday. While this low is deep, it is slowly starting to
fill, a few millibars at a time. Saturday expect storm to gale
force winds. Looking into Sunday, another low begins to track
along the western Aleutians with gusty winds up to gale force and
more rain showers.

&&

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

The long term forecast starts with a highly amplified pattern as an
upper level low situated over the Bering takes shape early
Tuesday. Meanwhile, two upper level ridges of high pressure flank
this low, one over the far western Bering, and a second over the
Alaska- Yukon border. For Southcentral, this "blocking" ridge over
the border will create a southerly track for moisture to advect
northward, so would expect unsettled and wet conditions to
continue into next week. By Wednesday, there is relatively good
model agreement that a deepening upper level low over Siberia will
develop and track eastward over the northern Bering. This will
ultimately create a more zonal flow pattern for the southern
Bering and Aleutian Chain, and will introduce a warm and wet air
mass to the Chain for Wednesday with accompanying gusty westerly
winds. By Thursday, a mostly stagnant area of low pressure over
the northern Gulf will usher several upper level waves northward
over Southcentral, resulting in continued southerly flow and
unsettled conditions. Overall, the pattern looks to be active and
unsettled for most of next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 170 173 175-178 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...MF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
LONG TERM...KO