Small Craft Advisory 892, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
512 PM AKST Wed Nov 9 2022

.ANALYSIS AND UPPER LEVELS...

The jet stream runs across the Bering and then dips south into the
north Pacific and then stretches to the north again through the
Gulf. Satellite shows a low pressure system southeast of Kodiak
Island and a front moving across the northern Gulf. Ahead of the
front, barrier jet winds of 35 to 55 knots have been observed.
Radar shows widespread rain near the coast and snow across the
eastern Kenai Peninsula with a few snow showers on the western
side and then snow backed up against the western Alaska Range.
Another band of snow is also seen across the Susitna Valley with
light snow reported at Skwentna and Talkeetna. Also some very
light snow spilling over the Chugach mountains near Anchorage.
Across Southwest Alaska light snow is depicted on radar from north
of Dillingham and eastward towards King Salmon. This snow is
associated with a deformation zone northwest of the low over the
southern Gulf. Across the Bering, there is fairly quiet weather
with westerly flow with a weak shortwave moving across the eastern
Bering and towards the Kuskokwim Delta. And finally a fairly
strong low pressure system south of the western Aleutians is
moving northeast towards the central Aleutians.

&&

.MODEL DISCUSSION...

Models are in good agreement with the low moving east across the
Gulf and the front across the northern Gulf moving inland this
evening. The models seem to be handling the downslope okay, but
are struggling with the occasional snow showers that move into
Anchorage, Kenai, and Soldotna areas. Models are also in good
agreement with the next low pressure system and front moving near
the Aleutian chain and into Southwest Alaska and the Gulf Thursday
and Friday. By day 3 Saturday there are some minor differences on
the track of a low across the eastern Bering, but these
differences are not expected to affect the overall weather impacts
to Southwest Alaska. The biggest forecast challenge will be
precipitation types, rain versus snow, across Southwest Alaska
late Thursday into Friday and Southcentral for Saturday due to
warm southerly flow.

&&

.AVIATION...

PANC...VFR conditions are expected to decrease to MVFR by early
tomorrow morning before lifting later in the morning back to VFR.
Occasional light snow is expected through tomorrow with little if
any accumulations that could periodically decrease visibility to
3 to 5 miles. Otherwise northerly winds at 5 to 10 kts expected
through tonight becoming light and variable by tomorrow morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Tonight through Saturday)...

Southcentral Alaska will see a brief period of quieter weather
tonight through Thursday, then a warmer and wetter pattern takes
hold from Friday through Saturday. An occluding low is currently
near Kodiak Island. With the low moving east across the Gulf of
Alaska and higher pressure building in, we'll see snow and winds
gradually taper off across the region through tomorrow.

By Friday morning, a low moving along the Aleutian Chain will
push its front into the Western Gulf. Gale force winds and
plentiful moisture will accompany this front as it sweeps across
the Gulf and into Southcentral from Friday through Saturday. Winds
and heavy precipitation will be the primary concern with this
system. We could see similar weather to what was experienced over
the past few days, with a barrier jet developing along the North
Gulf coast and elevated winds through Turnagain Arm. The influx of
warm air with this front will likely mean a return to rain for
some locations, especially along Prince William Sound and up Cook
Inlet. Overall, this could be a prolonged heavy precipitation
event, especially with continued southerly flow behind the front.
There remains some uncertainty with the timing of this front and
where exactly the rain/snow line will fall. However, confidence is
high that we'll see higher temperatures (approaching the high 40s
in some locations) and heavy precipitation along Prince William
Sound and Eastern Kenai Peninsula. For now, downsloping looks to
keep Anchorage and Western Kenai Peninsula dry.

&&

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

A strong surface low in the western Gulf of Alaska continues to
support an area of deformation aloft over the eastern portions of
Bristol Bay and the Lower Kuskokwim Valley. Light precipitation in
association with this feature will shift east this evening,
leaving only light snow showers hanging up along the Western
Alaska Range overnight. A weak surface low tracking into the
Kuskokwim Delta this afternoon will also bring a brief round of
light snow showers to the area through this evening. A weak front
extending south of the low will enhance shower activity along the
north side of the Alaska Peninsula overnight as well. Otherwise,
tonight into Thursday will be quiet as a shortwave ridge moves in
from the west. Temperatures will be able to cool, particularly
over inland areas where lows will drop back into the teens under
partly clear skies and light northwesterly flow.

Conditions become more active Thursday night as a front moves in
from the Bering Sea. This package, its arrival is now anticipated
earlier, with southeasterly winds gusting to gale force first
along the Alaska Peninsula on Thursday, before moving into
Bristol Bay for Thursday night. Temperatures should warm quickly
once the wind picks up, with highs again pushing 40 degrees in
Bristol Bay and mid to upper 40s along the Alaska Peninsula. Along
the leading edge of the front, a brief period of snow and blowing
snow is expected, where 1 to 2 inches of snow accumulation is
possible along the Bristol Bay coast west of King Salmon Friday
morning. However, snow will transition to rain for most of Bristol
Bay by Friday afternoon. The front sweeps north, out of Southwest
Alaska Friday night, but showery precipitation will continue as
the core of the low tracks through the region. Rain continues in
Bristol Bay overnight, with snow in the Kuskokwim Valley. Showery
precipitation continues area-wide as moist, southerly flow remains
in place into the weekend.

&&

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

A strong low south of the western Aleutians has begun to push a
storm-force front and moderate-to-heavy rain across the Aleutian
Chain this afternoon. Strong winds and intense rainfall reach the
eastern Aleutians early Thursday morning as the low tracks slowly
eastward south of the islands. Winds should subside below storm
force by the time they reach Unalaska and the Alaska Peninsula,
but terrain channeling may allow for areas of higher winds. Rain
also reaches the Pribilof Islands on Thursday as the front pushes
deeper into the Bering Sea. The system will continue east on
Friday while slowly weakening. Rain is expected through Saturday
for most areas along the Aleutian Chain as the low evolves into a
broad gyre with multiple centers of circulation and a quasi-
stationary front sets up across the southern Bering.

&&

.LONG TERM FORECAST (Days 4 through 7: Sunday through Wednesday)...

Looking ahead in the extended forecast, model runs are in decent
agreement with the evolution and progression of synoptic scale
features. However, model spread begins to grow in the specific
details towards the end of the period. Heading into the weekend, a
well pronounced upper trough is positioned from the Bering Sea
southward, with a low pressure system approaching the Alaska
Peninsula and Kodiak Island. A southerly flow pattern favors the
moisture and precipitation into portions of the north gulf coasts
and surrounding high elevations of Southcentral. Depending on the
track and position of the low, this system may produce an area of
gale to storm force winds offshore along Prince William Sound and
the Copper River Delta. Meanwhile, a weakening low near Bristol
Bay will likely keep wet conditions going for Southwest Alaska
until late Sunday. For early to mid- next week, a brief break of
drier conditions gets underway as an anomalous ridge of high
pressure prevails over mainland Alaska and northwestern Canada.
With this ridge pattern, above normal temperatures are looking
favorable across the state. Out west, a system reaches eastern
Russia that may produce a broad area of precipitation along with
some strong winds for the western Bering Sea. However, there is
low confidence in the details for the western Aleutians.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Special Weather Statement...101, 111.
MARINE...Storms...173-178.
         Gales...119, 130, 131, 132, 150, 155, 160, 165, 170-172, 179,
                 180, 352, 411, 412, 413, 414.
FIRE WEATHER...NONE.

&&

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