Gale Warning 29, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
458 AM AKST Mon Jan 2 2023

.ANALYSIS AND UPPER LEVELS...

A broad longwave trough remains nearly stationary over the
eastern Bering and western portion of Alaska. A vertically stacked
low located over Chirikof Island is helping to anchor the
aforementioned trough in place. Multiple shortwaves continue to
rotate around this low resulting in a surface low developing east
of Kodiak Island. Satellite Imagery depicts this low tracking
northwest towards the Kenai peninsula for this morning, keeping
conditions unsettled across the southern half of Southcentral.
Radar is displaying returns over the Kenai Peninsula and western
portions of Cook Inlet early this morning as the aforementioned
surface low pushes inland. Out west, various shortwaves rotating
around the backside of the trough will keep colder air locked in
place over the Bering and Aleutians along with occasional snow
showers.

&&

.MODEL DISCUSSION...

Models remain in relatively good agreement through Tuesday.
Guidance is keying in on the next low and upper-level wave to move
to the Kenai Peninsula this morning, helping to enhance another
round of light precipitation over Cook Inlet and across parts of
Anchorage and the Mat-Su Valleys. Hi-res models and most global
models are also indicating at the development of an inverted
trough across Southwest Alaska this afternoon, as the
aforementioned wave continues to push farther inland. This
development may be enough to change the pressure fields and bend
the Turnagain wind into Anchorage for a couple of hours, but
confidence on this is low. This would introduce other forecast
challenges such as temperatures and precipitation types as well.
Models then struggle Tuesday into Wednesday with the development
of a surface low in the eastern Gulf tracking northwest to the
Kenai Peninsula. The EC and GEM have one distinct low moving into
the eastern Kenai for Wednesday morning with precipitation
overspreading coastal Southcentral and Cook Inlet. The GFS and NAM
are showing two separate lows, both taking the first low as a
more southern track toward the Barren Islands for Wednesday while
the NAM has the second low tracking towards Prince William Sound,
and the GFS has it tracking towards the Seward area on the Kenai
Peninsula. The consensus between all of the models is that the
overall pattern favors a continuation of unsettled weather across
the region.

&&

.AVIATION...
PANC...VFR conditions will persist. There is a slight chance that
a southeasterly Turnagain Arm wind may bend across the terminal
this afternoon.

&&

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

The large, complex low in the western Gulf of Alaska is the main
source of most of the weather around Southcentral today. Multiple
centers in this complex can be seen with one just southeast of
Kodiak Island and another near Seward are the two biggest as seen
on satellite early this morning. This is causing some short-term
northeast flow west of these lows, but the southeast flow aloft
will return as the low near Seward heads westward this morning.
This southeast to east flow aloft is creating downslope
conditions for the lee sides of the mountains for most of
Southcentral and that trend will continue through most of today
into Tuesday. Coastal areas ill see rain at sea level and then
the change to snowfall as one gains elevation.

The forecast becomes quite a bit less certain Tuesday into
Wednesday for the Gulf region as the next set of lows is giving
the models absolute fits. Therefore timing of the precipitation to
the Gulf coast as well as the associated areas and strength of
winds in the marine areas is more uncertain than usual. There are
a number of Gale warnings for Tuesday over the Gulf of Alaska
waters, but these may need to be adjusted for both location and
strength as the lows develop and a better handle on their moves is
ascertained. For inland areas of Southcentral, the downsloping on
the lee side of the mountains is likely to continue keeping it
mostly dry and continued mild as far as temperatures go.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: This
afternoon through Wednesday afternoon)...

A generally unsettled pattern across Southern Alaska continues.
Despite this, impacts to populated areas seems minimal through
mid-week. A low currently crossing the AKPen from the Gulf of
Alaska into the Bristol Bay area will promote showers from the
AKPen to the Kilbuck Mountains, with likely precipitation from
Dillingham north until Tuesday morning. Precipitation type is
expected to remain as snow across the region throughout the
period, with a slight chance for wintry mix between Nondalton and
Igiugig early today. Snow accumulation from this system will be
light. Steady offshore flow and cloudy skies will persist through
Wednesday across Southwest Alaska as the aforementioned low parks
over the Bristol Bay/AKPen area. Temperatures will also hold
steady through mid- week with only slight deviations.

&&

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

The unsettled pattern seen across Southern Alaska holds true for
the Aleutians early this week as well with relatively more
impactful weather incoming. Currently a low crossing the AKPen
into the Bristol Bay area is creating showers along the Eastern
Aleutians. These showers will be producing intermittent periods
of snow from Unalaska to Port Heiden through Tuesday morning.
Brief showers may reach up to the Pribilofs however they are not
expected to persist. The low sitting over the Bristol Bay area
will draw slightly cooler air down the Bering over the Pribilofs
by Tuesday, however flow is not very strong and is expected to
diminish by Tuesday morning as the low weakens. Light to heavy
freezing spray is expected from the Pribilofs north, with heavy
spray most prevalent beginning about 100 nm north of Saint Paul.

Tonight, the next system to enter the Bering will be an elongated
frontal boundary originating from the Kamchatka Peninsula with
multiple embedded lows approaching the Western Aleutians tonight.
This front will bring widespread light to moderate precipitation
across the Western to Central Aleutians through Tuesday evening.
A lack of strong cold air moving in behind the front does ease
concerns for strong winds associated with this system.
Precipitation will likely fall as snow with pockets of wintry mix
possible however less pronounced. By Wednesday morning, the front
will lose organization and the embedded lows will break apart the
overall flow pattern. Following the break-up of the front, model
discrepancies have strained forecast confidence. The next
system on the horizon is actually the parental low from the
aforementioned front. This Kamchatka low will reinvigorate the
unsettled pattern and make it's approach to the Western Aleutians
by Thursday afternoon.

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

Looking into the extended forecast, the active weather pattern
that both the Bering Sea/Aleutians, Southwest, and Southcentral
Alaska has experienced in the near to short-term looks to continue
through the long-term as well. Overall ensemble guidance and
deterministic guidance is in decent agreement that the entire
domain remains withing the influence of the upper trough pattern
that has been the status-quo of late. While there is general
agreement on the upper synoptic long-term pattern, surface
features and their evolutions (timing, track,
precipitation/precipitation type) remain up for debate.

The pattern for the Bering and Aleutians features an upper level
low complex that remains nearly stationary as it spins in the
western Bering Sea Wednesday through Saturday. Multiple shortwaves
rotate cyclonically around the complex and draw up Pacific
moisture from the south and southwest. The forecast challenge will
be nailing down where surface low pressures might spin up in
response to the various shortwaves as well as cold air
availability. The synoptic pattern supports an active and wet
western to central Bering/Aleutian Chain with not quite as active
of a pattern for Southwest. Although, there will be shortwave
troughs that move in from the Bering; especially for Thursday and
Friday. The North Pacific side of the Alaska Peninsula looks to
stay on the active side mostly due to moist southerly to
southeasterly upslope flow. Odds tilt that temperatures as well
as precipitation will around normal for Southwest and the Bering
Sea/Aleutians, regardless of the continued active weather pattern.

The pattern for Southcentral features continued southerly to
southeasterly moist flow which will keep coastal sections of
Southcentral unsettled. A notable potential surface feature that
will need to be watched will be a Gulf of Alaska low near Kodiak
Island that has the potential to bring a storm-force barrier jet
with it to the northern Gulf Coast. Another feature of note which
has decent guidance agreement is a negatively tilted trough which
extends from an upper level Bering low that will enter the Gulf
during the day on Saturday. Kodiak Island and the eastern Kenai
Peninsula will need to follow the progression of the forecast
regarding this feature for possible impacts down the line.
Ultimately, the general long-term synoptic pattern favors an
active coastal Southcentral; especially western Prince William
Sound and eastern Kenai Peninsula with odds leaning slightly
towards above average precipitation. Meanwhile, interior areas
look to have normal precipitation with not quite as much activity
as the coast due to potential cross-barrier downslope flow.
Temperatures look to be around normal for Kodiak Island, the
Kenai Peninsula, Mat-Su Valleys, and Anchorage, while odds tilt to
slightly above normal temperatures for Prince William Sound
communities and the Copper River Basin.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 119-120, 351.
		 Heavy Freezing Spay Warning: 180, 185, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...NSC
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CL
LONG TERM...CJ