Gale Warning 676, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 PM AKST Fri Nov 18 2022

.ANALYSIS AND UPPER LEVELS...

Strong high pressure continues to stretch from western Canada and
towards the interior of Alaska with it bowing towards Southwest
Alaska and the eastern Bering. A pair of low pressure systems are
moving out of the north Pacific and into the Gulf these will
eventually bring rain and snow near the coast this weekend. Radar
is quiet with no echoes observed across the area. Temperatures
are below zero across the Copper River Basin with teens and
twenties across most populated areas of Southcentral and
temperatures in the 40s above 1,000 feet or so as a strong
inversion is still in place. Otherwise near the coast temperatures
are a bit warmer mainly in the 30s to near 40. South of the
western Aleutians another low pressure is tracking south of the
Aleutians through the weekend. Otherwise quiet across most of the
west with light rain reported at Bethel and across the southern
Alaska Peninsula with temperatures mainly in the 30s and 40s
across most of the Aleutians, Pribilofs, AKPen, and Southwest
Alaska.

&&

.MODEL DISCUSSION...

Models have come into better agreement through Sunday morning as a
pair of low pressure systems moving northward across the Gulf
bring rain and snow near coastal locations. The models have
locked on to the western track of the second low towards the
eastern Kenai Peninsula Saturday into early Sunday. By Sunday
afternoon through Monday another upper level shortwave with
surface low moves across the Gulf, but there is more uncertainty
with the track and intensity of this surface low as the GFS is
much deeper with the EC showing an open wave while the NAM and GEM
show weaker lows. The forecast challenges through the weekend
will be the slight possibility of freezing precipitation across
interior valleys of the eastern Kenai Peninsula with the onset of
precipitation on Saturday, however if any does occur it will
likely be short-lived as the inversion weakens and warmer air is
expected to move inland as the easterly winds increase ahead of
the low. The other challenge will be the possible development of patchy
fog tonight for some interior valleys, but hard to pin down where
it will form.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through the
TAF package. There is a chance of fog and low clouds
tonight/tomorrow morning at IFR or below as it has been observed
over the Knik River and Turnagain Arm today.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
tonight through Monday)...

Evening satellite imagery shows a lead-wave trough lifting into
Southeast Alaska with high clouds moving into Prince William Sound
and over Cook Inlet. Southcentral experienced predominantly clear
skies today, although some pesky areas of fog persisted along the
Turnagain Arm and across the Copper River Basin through the
morning hours. Some fog will again be possible tonight into
Saturday. Otherwise, changes to the forecast are in store for
Southcentral as a ridge of high pressure, responsible for several
days of clear skies, finally begins to break down. Expect
increasing cloud cover to continue overspreading Southcentral
through the weekend. Rain chances will be confined to coastal
regions and Prince William Sound through Saturday. Some
uncertainty remains with regard to ptypes across the eastern side
of the Kenai Peninsula. While the bulk of precipitation should
fall as rain, a brief period of freezing rain may develop with
negligible accumulations later tonight. Continued warm air
advection into the coast should see temperatures climb to above
freezing through the rest of the weekend.

An upper low then approaches the coast late Saturday into Sunday,
helping to reinforce rain chances. Offshore winds oriented
parallel to the coast will aid in the development of a barrier jet
and gale force winds through the day on Saturday. These winds
will gradually diminish through Sunday morning as low pressure
lifts inland of the coast. Kodiak can expect to see northeasterly
winds at or above 30 mph for most of Saturday as well. Finally,
Sunday into Monday rain chances for Southcentral will attempt to
expand further inland, though strong easterly flow over the
mountains should downslope precipitation and limit any moisture
outside of the Chugach and Kenai Mountains.

&&

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

Drier and cooler conditions are in store for Southwest Alaska
through Monday. The shortwave currently extending across the
Kuskokwim Delta and Alaska Peninsula will depart to the west
tonight, bringing an end to rain. However, the fog that has
developed over Kuskokwim Delta may linger through tonight and into
tomorrow morning in the absence of stronger winds to help mix it
out. Other parts of Southwest Alaska should see a few hours of
clearer skies tonight into tomorrow morning.

Clouds will increase from south to north beginning Saturday
morning as a Gulf low moves towards the Eastern Kenai Peninsula.
The bulk of moisture will remain along the North Gulf coast, so
most of Southwest Alaska should stay dry. The exception will be
along the Alaska Peninsula, where an occluded front will bring
rain showers as it tracks eastward from Saturday through Sunday.
Precipitation chances increase across Southwest as the occluded
low itself arrives at the Alaska Peninsula on Sunday night.
Otherwise, expect temperatures to trend colder over the next few
days as northerly flow helps usher in cooler air.

&&

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

Active weather is in store for the region through Monday as an
occluding low tracks east across the Aleutian Chain and Alaska
Peninsula. Expect light rain and winds largely below small craft
speeds ahead of the low. As the low continues to occlude,
precipitation should become more showery and sporadic in nature.
The bigger story will be northerly winds and cold temperatures
along the backside of the low. Gale force winds will persist along
the Western Aleutians and Bering Sea through Saturday evening. As
an upper level trough pushes into the Bering Sea from the west,
this swath of gale force winds will strengthen and begin to track
eastward. Model differences with the speed of the upper level
trough make it difficult to ascertain how quickly these northerly
gales will move eastward, and it's possible that locations such as
the Pribilof Islands could see winds reach small craft speeds or
greater as early as Sunday night. What we have greater confidence
in is that the Western Aleutians and Bering will begin to see
nighttime lows dip towards freezing by early Monday morning.
Colder air temperatures in combination with strong winds and low
sea surface temperatures mean that freezing spray is likely in
the Northern Bering Sea.

&&

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

Looking ahead in the extended forecast, the latest model runs and
ensemble guidance are in fairly decent agreement with the
evolution and progression of the synoptic features. The strong
upper ridge over mainland Alaska breaks down at the start of the
period, but will help deflect the main storm track to the south.
At the start of the period, a series of low pressure systems are
expected to track from the North Pacific into the Gulf of Alaska.
Because of the small to mid-scale interaction of embedded features
moving upstream, models have yet to iron out the intensity and
track of these systems for the coastal areas of Southcentral.

The first deep low moves into the central Gulf Monday through
Tuesday, with heavier precipitation pushing onshore along western
Prince William Sound (PWS) and eastern Kenai Peninsula. This
system may develop a barrier jet along the north gulf coast and
downslope the amount of moisture streaming inland. By Tuesday,
precipitation increases across the inland valleys and throughout
the mountainous areas as the low moves between Cook Inlet and PWS.
A second deep low moves into the eastern Gulf Wednesday through
Thursday, with most of the precipitation along eastern PWS and 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 scattered showers 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. The
GFS/EC/CAN are advertising a deep surface low and front with
increasing warm, southerly winds that will impact the western
Bering/Aleutians during the middle part of next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 119, 120, 131, 177, 178, 185, 351, 411.
FIRE WEATHER...NONE.

&&

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