Gale Warning 537, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
654 PM AKDT Tue Sep 27 2022

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

An upper-level low centered near the Central Aleutians is
forecasted to track along the Alaska Peninsula and into Southwest
Alaska over the next few days. By Wednesday morning, the low
center will reach the Eastern Bering/Kuskokwim Delta Coast and
then linger around that area before diving south and exiting into
the North Pacific late Thursday night into Friday. The low's
attendant front has already reached the Southwest coast and will
continue pushing inland before disintegrating on Wednesday.

Given the current synoptic setup and evolution, southeasterly
gale force winds south of the Alaska Peninsula and easterly winds
across Bristol Bay will persist through Wednesday morning, after
which time they will gradually diminish. Then, southwesterly gale
force winds will briefly develop on both sides of the Alaska
Peninsula Thursday morning, thereafter diminishing with the exit
of the low. Rainfall will spread across the entire region through
most of Thursday, and conditions are expected to improve for late
Thursday night and Friday, with brief showers still possible along
mountain ridges.

&&

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

An upper-level low currently located near the Central Aleutians
will track east to Southwest Alaska over the next few days. Gale
force winds along the backside of the low, or across the Central
Aleutians and Eastern Bering, will gradually track east with the
low through late Thursday night. A ridge of high pressure over the
Western Bering and Aleutians will continue building to the east
behind the low, yielding clearing skies and drier conditions for
much of the region through Thursday morning.

Around Thursday afternoon, all eyes shift to the Western Bering
and Aleutians as a powerful storm system is expected to enter the
domain. The remnants of Tropical Storm Kulap, which is currently
in the West Pacific, will comprise the strong low presure system
forecasted to impact our western domain. Models illustrate the
most likely track taking the low across the Western
Aleutians/Bering from Thursday afternoon through Friday. Then, the
storm is advertised to move east and weaken as it enters the
Central Bering late Friday night. Southeast winds are expected to
increase Thursday morning across the Western Aleutians and then
shift southwest late Thursday night over the same area. The
highest winds are currently expected near Attu Island early Friday
morning, where gusts to 100 mph are possible. Widespread
sustained (storm force) winds are expected to be around 60 to 75
mph. Thus, a High Wind Watch will take effect from Thursday
afternoon through Friday afternoon for the Western Aleutians.
Fortunately, once this storm enters the Bering Sea, it is unlikely
that the low will take a similar track to that of the Typhoon
Merbok remnants. Stay tuned to the forecast for updates on the
upcoming storm.

&&

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

The pattern continues to be active in the short-term period with
continuous moist southerly to southwesterly flow aloft. As a
result, a plethora of rain chances looks to be on tap, especially
for the eastern Kenai Peninsula and the Prince William Sound area.
An upper level and associated surface low continue to move
eastward across the across the eastern Aleutians towards the
Alaska Peninsula and eventually into the Bristol Bay area. As it
does so, the low's warm front will lift/pivot towards the
Southcentral coast for Wednesday morning. Kodiak Island will
start seeing rain today as the system progresses northward. The
precipitation winners look to be the Prince William Sound area as
well as the eastern Kenai Peninsula. The western Kenai Peninsula,
Anchorage Bowl, and Mat-Su valley will see less rain due to
cross- barrier/downsloping southeast flow. Freezing levels look to
hover around the 2000-2200 foot mark this evening in the Copper
River Basin with daily minimum temperatures and snow levels on a
rising trend through the short term as the warm front approaches.
Therefore, frozen precipitation looks of minimal concern. Expect
continued precipitation chances through Friday as passage of upper
level shortwaves continue, especially for Prince William Sound
and the eastern Kenai Peninsula.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Thursday night)...

A cold, crisp and calm start to the day is unfolding for most of
the region. Clear skies overnight coupled with already cool low
level temperatures and nearly still air have allowed temperatures
to dip down to or near the freezing mark over the valleys of
Bristol Bay, with 30s common elsewhere. A few patches of fog will
be possible through the late morning, but otherwise more inclement
conditions will hold off until later in the day. By this afternoon
and evening, a low moving along the Aleutian Chain into the Alaska
Peninsula (AKPen) will send a front northward across the outlook
area. Increasing temperatures along with Rainy and blustery
conditions will follow ahead of the front as it lifts north,
particularly through gaps and passes along the Aleutian/Alaska
Ranges. Southeasterly winds will become especially strong where
synoptic flow will align favorably for enhanced gap winds through
the Kamishak Gap through tonight. Easterly gusts are expected to
peak at around 35 to 45 mph for areas including Iliamna,
Koliganek, and Igiugig late tonight into early Wednesday morning.
In addition, rain will be most intense over areas influenced by
upslope enhancement, namely along the Kilbucks and areas just
south including Dillingham through Wednesday morning.

Looking farther into Wednesday and beyond, an unsettled, showery
pattern will continue as the aforementioned low drifts very slowly
northeast near the Kuskokwim Mountains and slowly weakens.
Southeast winds will cut out Wednesday night as the low's front
disintegrates and the east to west pressure gradient slackens.
Periods of rain showers will continue well into Thursday as the
upper level low remains centered overhead and as individual waves
of energy rotate around the main upper level low and kick off
showers in a continued dynamically (and perhaps slightly
convectively) unstable environment. We should finally see things
dry out a bit by Thursday night as the low shifts southeast across
the AKPen and towards the Gulf.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Today through Thu night)...

A gale force low and attendant front will continue to make steady
progress east throughout the day today, with most of the stronger
winds sharply confined along just the frontal boundary and
towards the back side (western edge) of the low. Gusty
southeasterly winds and rain along the southern Alaska Peninsula
(AKPen) should cut off rapidly as the front pushes quickly
northeast through the morning. Conversely, winds will pick up
rapidly across the central Aleutians as a core of northerly gale
force winds supported by decent cold air advection and an enhanced
pressure gradient on the trailing portion of the system advance
east with time. The change in winds will be notably abrupt as the
corridor of stronger winds approaches, with nearly calm conditions
shifting suddenly to northerly gusts of 30 to 40 kts for places
like Atka, Nikolski and Dutch Harbor at some point between now and
this evening. Blustery northerly winds up to gale force will
continue for mainly the eastern Aleutians and southern AKPen
through Thursday morning as the upper low stalls out to the east
over Southwest Alaska. In the meantime, a weak low will push a
quick-hitting round of rain across the far western Aleutian Chain
early on Wednesday. More showery precipitation will persist near
the more unstable conditions to the east through Thursday with
cool temperatures advecting over the seasonably warm sea surface.

Attention then shifts to the powerful storm system expected to
enter the southwest corner of the Bering by Thursday afternoon.
This low pressure system will be what's left of what is currently
tropical storm Kulap, a tropical cyclone moving across the West
Pacific. Models are beginning to get a better handle on how this
storm will interact with a separate upper level through ejecting
into the Bering from the Sea of Okhotsk. There is increasing
confidence for the resulting phasing or merger of these two
systems to result in a very powerful low that will mature in
intensity as the center moves just west of Shemya by Thursday
night. Winds along the low's front will push well into storm force
range with gusts to Hurricane force possible during the afternoon
on Thursday across mainly far western portions of the Aleutian
Chain. Winds will up with ferocity from the west in the same area
after only a short break Thursday night as a core of even stronger
winds on the south side of the low passes over the far
southwestern Bering. Sustained winds of Hurricane force will be
possible with this second batch of winds in the vicinity of Shemya
on Thursday night, with gusts perhaps peaking as high as 80 to 90
kts. Fortunately, there are still no indications this low will
take a similar track to Merbok, and the current expectation
remains for this low to slow to a crawl over the central Bering as
it fills in and weakens through the end of this week.

&&

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

Looking ahead in the extended forecast, the latest operational
model runs are in a decent agreement, but begin to diverge in the
specific details towards the end of the period. The main feature
heading into the weekend will be a deep area of low pressure
moving through Bering Sea from remnants of Kulap. This system
continues to bring strong winds and moderate to heavy rain along
and ahead of the front across the Aleutian Chain, Pribilof
Islands, and Southwest Alaska. By Sunday, the low turns southeast
and weakens as it tracks towards the Alaska Peninsula. Another
storm system, albeit weaker, approaches the central and western
Aleutians with the next round of wind and rain for early next
week. Unsettled weather continues into Tuesday as a North Pacific
low lifts toward the Kamchatka Peninsula. However, models diverge
significantly in the low placement and strength. Meanwhile, a
transient ridge of high pressure provides a brief break of drier
weather early Saturday over Southcentral. The aforementioned
Bering front will then shift into the northern gulf and then into
the southern mainland for a return of cool, cloudy, and rainy
conditions.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch 191,
MARINE...Gale 119 120 125 132-138 141-174 176 180 185.
		 Storm 130 131
FIRE WEATHER...NONE.

&&