Gale Warning 675, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
458 PM AKST Thu Nov 17 2022

.ANALYSIS AND UPPER LEVELS...

Starting on the west side a broad area of low pressure resides
across the western and northern Bering with a weakening frontal
system stretching from St Lawrence Island to the central Aleutians
with relatively light winds of 15 knots or less and occasional
light rain. Temperatures across the Bering and Aleutians are in
the upper 30s to low 40s. Farther east moisture is pumping into
the Alaska Peninsula and Southwest Alaska with a shortwave moving
towards the Kuskokwim Delta. This feature is causing light rain
with temperatures in the 40s across Bristol from Port Heiden and
Pilot Point to Dillingham and Togiak and the mountains north of
there, which is depicted on radar. Winds from the southeast
continue to be observed at 20 to 30 knots across Southwest Alaska
due to a stronger pressure gradient. Across the Gulf and
Southcentral a large high is centered near Southeast Alaska with
the ridge extending into the interior of Alaska. Satellite shows
mostly clear skies across much of the area, however low stratus
clouds are seen across the Copper River Basin as well as across
the southwest Gulf extending towards Kodiak Island and the Barren
Islands. Temperatures across Southcentral range from below zero in
parts of the Copper River Basin to single digits to low 20s
across most other lower elevations sites. However, above the
inversion in higher elevations temperatures are in the upper 30s
and 40s.

&&

.MODEL DISCUSSION...

Models are in pretty good agreement through Friday with the
shortwave moving towards coastal areas of Southcentral. Models
continue to show differences in the track of a low pressure
system moving across the Gulf on Saturday through Sunday. Both
the EC and GEM show the low farther east moving onshore near
Cordova, while the GFS and NAM have the low farther west moving
towards the eastern Kenai Peninsula. Out west models agree well
with a low pressure system tracking south of the Aleutians through
Sunday and a trough moving out of Russia towards the northern
Bering late Sunday into Monday. The biggest forecast challenge
will be timing the precipitation across coastal locations in
Southcentral.

&&

.AVIATION...

PANC...VFR conditions and light northerly winds will persist
through the TAF package.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3/Tonight through Sunday morning)...

A sunny day was had across much of Southcentral on Thursday as
high pressure continues to dominate the forecast area. While much
of the region, especially at the lower elevations, experienced
continued at or below freezing temperatures, warmer conditions
were found at the higher elevations. One notable location, Glen
Alps, reached a sweltering 52 degrees by mid afternoon. Meanwhile,
further east, coastal locations across Prince William Sound
remained in the mid to upper 40's. Cooler temperatures were
experienced further east and across much of the Copper River
Basin. Many locations were stuck beneath persisting fog and low
stratus with temperatures across Glennallen struggling to climb
above zero degrees. Fog will likely continue to be a nuisance
through tonight, but as high pressure begins to break down fog
should diminish.

An expected pattern change will commence over the next couple of
days, as a shortwave trough, tracking northward along the eastern
Gulf coast, begins to break down high pressure over Southcentral.
This will also bring renewed precipitation chances to the Gulf
coast late Friday into early Saturday. The initial shortwave will
be followed by a larger upper low and front on Sunday with shower
chances expanding across Prince William Sound and the Chugach
Mountains. Snow chances look dim for all but the higher elevations
tonight through the weekend, with snow levels rising further to
above 2,000 feet Saturday evening. Currently, it looks like areas
further inland will remain largely dry, though a light rain/snow
mix may be possible over Anchorage on Sunday if moisture does
breach the coastal mountains.

As mentioned in the previous discussion, there remains some
uncertainty with the overall track of the low on both Saturday and
Sunday, though guidance is slowly coming into better agreement.
The low itself may hang up over northern Gulf on Sunday before a
second shortwave trough pivots cyclonically into the Kenai
Peninsula. As such, Kodiak could see an extended period of rain
and elevated northeasterly winds from Saturday into Monday
depending on how long the low lingers over the northern Gulf.
Forecast wind gusts as high as 30 mph will be possible during the
late morning hours on Saturday as a potential barrier jet
develops, with the axis of the highest winds being directed along
Kenai Peninsula coast, into northern Kodiak Island and the
Shelikof Strait.

&&

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

Relatively quiet and cooler weather is in store for Southwest
Alaska through Sunday. Rain will continue through tomorrow morning
along the Kuskokwim Delta and Alaska Peninsula as an upper level
shortwave moves across the region. As the feature departs,
Southwest Alaska should experience a few hours of clearing skies
on Saturday. However, clouds will gradually build in from
southeast to northwest ahead of a low moving into the Eastern
Gulf of Alaska. Northeasterly winds will also pick up across the
Kuskokwim Delta and Bristol Bay on Saturday and Sunday as the
pressure gradient tightens between a ridge over Mainland Alaska
and a low in the Bering Sea. While parts of the Alaska Peninsula
and southern Bristol Bay could see some showers with this low over
the weekend, the bulk of Southwest should stay dry if the low's
track keeps it further to the south and east.

&&

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

Much of the focus will be on the Western and Central Bering Sea
over the next few days as a broad, occluding low moves in from the
North Pacific. Winds and precipitation chances will begin
increasing tonight, with small craft winds and light to moderate
rain expected. By early tomorrow morning, winds will increase to
gale force over the Western Aleutians and Bering Sea and persist
through Sunday. There remains some uncertainty with how quickly
this area of gale force winds will move east into the Central
Bering and Aleutians. The current forecast package represents the
slower end of potential outcomes, so we may see stronger winds
move east more quickly on Sunday. For precipitation, expect
rain showers to trek eastward across the Aleutian Chain as the
front progresses, reaching the Eastern Aleutians by Saturday
morning.

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)

The strong upper ridge over Alaska breaks down and shifts east at
the start of the period. The main storm track will initially stay
to the south with low pressure systems tracking northward into
the Gulf of Alaska. Although there are timing and strength
differences with these features, a couple of upper level
shortwaves and surface lows brings precipitation and gusty winds
along the coastal areas of Southcentral. The first low moves in
the Gulf on Monday and should bring continued unsettled conditions
for the eastern Kenai Peninsula and Prince William Sound (PWS).
This system may develop a barrier jet along the north gulf coast
and limit the amount of moisture moving inland. By Tuesday,
precipitation increases across the inland valleys and throughout
the mountainous areas as the low moves between Cook Inlet and PWS.
Later in the week, a secondary low approaches the Gulf with most
of the precipitation and wind staying over the northern Alaska
Panhandle.

Out west, a deep trough and strong upper low over eastern Russia
moves southward into the Bering Sea between Monday and Tuesday.
Ahead of the trough/low, a cold front pushes across western Alaska
and brings light to moderate precipitation with below normal
temperatures. For the eastern Aleutians and Alaska Peninsula, the
main feature to note is the colder air advection promoting
localized gusty winds out of the bays and passes. Cold, northerly
flow over the relatively warm waters will also help generate
widespread showers over the Pribilof Islands and along the
Aleutian Chain. By midweek, an amplified ridge builds across the
western/central Aleutians before unsettled conditions returns with
another upper trough/low developing between Wednesday and
Thursday. Models have yet to iron out the intensity and track of
these troughs and ridges as well as the impacts for the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 120, 131, 138, 177, 178, 411
FIRE WEATHER...NONE.

&&

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