High Wind Watch 7, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
534 AM AKDT Sat Apr 16 2022

.ANALYSIS AND UPPER LEVELS...

There is an upper level ridge spanning from Prince William Sound
to the eastern Gulf Of Alaska. On satellite imagery there is a
low over the northern Bering with the remnants of a frontal
system pushing across the Alaska Range and Cook Inlet. There is
another low southwest of Attu and Shemya. Advanced
Scatterometer data (ASCAT) has detected gale force winds with this
low early this morning. The jet core is west of Adak with an
estimated magnitude of 170 knots. On satellite imagery (CIMSS
MIMIC PW) there is a fetch tropical moisture south of the western
Aleutians that extends into the Northwest Pacific Basin and the
remnants of former Typhoon Malakas. The radars at Bethel and King
Salmon have both detected light precipitation overnight.

&&

.MODEL DISCUSSION...

The run to run continuity with the NCEP models has been really
good. Overall models consensus remains with the synoptic pattern
for the next 60 hrs. By 00z Tuesday there is divergence involving
a low moving south of the Gulf Of Alaska and shortwave energy near
Kamchatka. All of the models hold onto a high over Prince William
Sound.

&&

.AVIATION...
PANC...VFR and light wind conditions will persist. Cigs got down
to 6,000 ft early this morning as the remnants of a frontal
boundary moves over Southcentral. The cigs are being monitored and
amendments will be made as needed.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3...Sat
through Mon)...

Quiet conditions will persist across much the area
through the weekend and into next week. High pressure continues
to be the dominant synoptic feature. The exception is a weakening
front stretching out over Kodiak Island. Just under an inch of
rain has fallen in Kodiak City in the past 24 hours with upwards
of a few more tenths possible by this afternoon. By this
afternoon, weak ridging will start to build back over the area and
help to push the remnants of the front west of the area. This
should also allow some of the cloud cover to start to dissipate
through the afternoon today.

The only other feature of note is a shortwave coming out of the
Arctic late tonight into Sun. A closed area of high pressure
centered near Utqiagvik will help to send that shortwave quickly
from the Yukon Territory down through the Copper River Basin. This
will be a fast moving system but will serve to reinforce some cold
air over the Wrangell Mountains. It could also help to trigger
some showers over the mountains, especially during the afternoon.
For some of the favored outflow areas, the shortwave will help to
increase the northeast winds through Thompson Pass with gusts to
around 35 mph. As that energy slides further south, we can't rule
out some showers along the Kenai Peninsula Sun afternoon. All in
all though, expect quiet weather with a fair amount of sunshine
for most areas for the next couple of days.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Tuesday morning)...

A weak front currently exists over Southwest Alaska and will
slowly move west while continuing to weaken through the day
today. Most of the precipitation will fall as rain over northern
Bristol Bay with snow likely above higher elevations. Bethel and
the Y-K Delta coast may see a shower or two as well. Expect
temperatures to remain at to above average over the next three
days as southeasterly winds continue to advect warmer air into the
region and cloud cover prevents radiational cooling at night.
Areas in the lee of the Western Alaska Range are the mostly likely
to see some sunshine as downsloping helps to dry out the
atmosphere, while areas along the coast will stay cloudy due to
another large system moving into the Bering.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS/ALASKA PENINSULA (Days 1 through 3: Today
through Tuesday morning)...

A vertically stacked low in the central Bering will continue to
weaken today before being absorbed by what was formerly Typhoon
Malakas. This storm will impact all of the Aleutian Chain and
Alaska Peninsula through Tuesday as it moves west to east across
the region. Widespread gales are expected along the front, with
storm force gusts over the Eastern Aleutians and Alaska Peninsula
west of Nelson Lagoon Sunday afternoon to early Monday morning.
On the backside of the low, expect storms to impact Adak and Atka
as another upper level shortwave reinvigorates the cold air
advection behind the low. Mostly rain is expected along the warm
sector with convective snow showers in the cold sector. The
Pribilof Islands will see a mixture of rain and snow throughout
the event, but most of the precipitation will remain south of the
area. The low is expected to depart into the North Pacific late in
the day on Tuesday, but strong northwesterly winds will remain
over the Central and Eastern Aleutians through most of the day.

&&
.Marine (Days 3 through 5: Monday through Wednesday)...

Gulf of Alaska: Generally calm conditions will prevail across
most of the Gulf with light winds and seas less than 10 ft
throughout the outlook period.

Bering Sea: The post-tropical remnant of former Typhoon Malakas
will essentially be an ordinary and weakening Bering low by early
next week, with the center expected to cross the eastern Aleutians
into the North Pacific on Monday. Expect widespread gale force
winds with this system Sunday through Monday, with good potential
for a small corridor of storm force gusts in both the southeasterlies
ahead of the low and northwesterlies behind the low. As with the
most recent storm, southeasterly winds will be particularly strong
through bays and passes along the southern Alaska Peninsula. The
extended duration of steady gales will maintain 15 to 20 ft seas
across the far southern Bering through early Tuesday, with up to
25 ft seas on the Pacific side of the eastern Aleutians.

Winds and waves will diminish in the wake of this storm Tuesday,
but there is potential for a large North Pacific low to enter
the southern Bering Sea and possibly undergo rapid deepening.
However, forecast uncertainty increases markedly for this next
system, and confidence for timing/location of higher seas and
winds is low at this point.

&&

.Long Term Discussion (Days 4 through 7: Tuesday through Friday)...

The outlook for next week deteriorates from reasonably clear to
very unclear remarkably quickly, with model agreement and run to
run consistency sorely lacking by the end of next week. What's
more clear is that a turn from mostly quiet to very active
conditions is becoming increasingly likely, especially out west.
Looking at the start of the period on Tuesday, what's left of
post-tropical Malakas should finally be exiting the picture as
the remnant low is steered southeast from south of the Alaska
Peninsula out to sea by strong northwest flow downstream from a
transient ridge developing across the Aleutians. Areas of rain or
rain/snow mix along the eastern Aleutians and southern Alaska
Peninsula should mostly shut off by Tuesday evening as the low
departs. Steady, light rain and snow along a stalled out frontal
axis stretching from near Dutch Harbor to St Matthew will hang
around a bit longer into early Wednesday as the front degrades.
Meanwhile, a stubborn blocking high centered up near the North
Slope will remain in place through at least Wednesday, while a
weak upper low drifts across the southern mainland within weak
easterly flow on the south side of the blocking high. Cool
mid/upper temperatures and weak lift around this easterly wave/low
will support isolated to scattered shower activity as it moves
across Southcentral on Tuesday and Wednesday, especially over
inland valleys lacking snow cover where afternoon heating will
be most effective.

Pattern details begin to fall apart for the latter half of next
week, with operational runs diverging significantly for the
progression and eventual interaction of two separate shortwave
troughs moving east/northeast towards the Bering from the
northwest Pacific. However, there are ever increasing signs
these two features will phase together as they reach the
Bering/Aleutians late on Wednesday or Thursday, supporting
potential for strong cyclogenesis and resulting development of
a large, powerful surface low near or over the southern Bering.
This low appears most likely to move east roughly along the
Aleutians between Wednesday and Thursday, then approach the Alaska
Peninsula or western Gulf by Friday. While it's difficult to get
into details due to major differences in model handling of this
system, it's likely we will see far-reaching impacts for much of
the forecast area from this system, assuming support continues to
grow for the scenario above late next week. This could range from
potential moderate to heavy precipitation, very strong winds, and
high seas for portions of the forecast area, depending on
how/where the system develops and tracks east. Check back for
forecast updates for the Wednesday to Friday timeframe as details
for this possible stronger system become more apparent.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 173
Gale Warning 170-172 174-179 411-414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CJ
MARINE/LONG TERM...AS