Small Craft Advisory 39, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
456 AM AKST Wed Jan 11 2023

.ANALYSIS AND UPPER LEVELS...

The low, with its center near the Kuskokwim Delta, is continuing
to track north while snowfall remains for many across Southwest. A
fairly dry shortwave trough is tracking through the eastern
Aleutians and thicker cloud cover has helped to clear some of the
fog that was being reported in Cold Bay last evening.

Winds are ramping up over the western Aleutians due to a large,
storm force low over the North Pacific that is slowly moving
northeast.

Southeasterly flow in the northern Gulf is bringing precipitation
to the eastern Kenai Peninsula and into Prince William Sound.
There is reflectivity near Valdez and Cordova appearing on radar,
but it is currently too dry at the surface for precipitation to
reach the ground.

&&

.MODEL DISCUSSION...

Synoptic agreement is good and slight variations in the details
have little implications to the general weather outcome. The North
Pacific low approaching the western Aleutians is expected to
stall and gradually weaken and could impact the length of time
for the western Aleutians that would remain in storm force. As
this low breaks down, multiple shortwaves are likely, but the
timing each wave is less certain, especially going into the end of
the week.

&&

.AVIATION...

PANC...Snow over Anchorage should remain light through this
morning and ceilings are expected to gradually lower today. Light
winds will prevail.

&&

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

A negatively tilted trough will move across the Kenai Peninsula
this morning this will bring a rain snow mix near the coast at
Seward and Cordova while areas farther inland and the higher
elevations will see snow. This trough will bring a brief round of
light snow across the Anchorage area and portions of the Mat-Su
valleys, however snow accumulations will be less than an inch in
most areas. This trough will move inland today with light snow
moving across the Copper River Basin before tapering off by this
afternoon. This evening the trough will move to the north while
weakening.

As we head into Thursday quieter weather is expected across inland
areas with a mix of clouds and sun during the daylight hours,
however temperatures will remain near normal for January. A low
pressure system over the north Pacific will bring a shortwave
across the Gulf on Thursday which will bring precipitation near
coastal areas with snow levels ranging from 500 to 1500 feet so
most sea level locations will see rain except for Valdez which
will stay all snow, however snow accumulations will be minimal.
Friday another trough rotates from the eastern Gulf into the
northern Gulf this will bring another round of rain and snow near
the coast. However there is more forecast uncertainty with this
Friday system.

&&

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

A few light snow showers will persist through the morning hours
across Southwest Alaska in the wake of yesterday's upper low. The
same low has since shifted north of the Kuskokwim Delta and into
the Bering, leaving behind weak onshore flow into the Kuskokwim
Delta and Bristol Bay. High pressure will build into the region
later tonight and persist into Friday night, which will help to
promote calmer and drier activity over the next couple of days.
The next chance for precipitation will develop over the weekend
with the arrival of a North Pacific low into Southwest Alaska,
though models are currently showing discrepancies on placement and
timing.

&&

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

Unsettled conditions are anticipated across the Bering and the
Aleutian Chain through the end of the week as a large upper low
shifts over the western Bering. This low will bring storm force
winds as well as widespread showers to the region as its front
slowly spreads eastward across the Aleutians. On satellite the
front has already begun to overspread the Western Aleutians.
Initial snow showers this morning may lead to a few inches of snow
before continued warm air advection ahead of the low changes snow
over to rain by this afternoon. Further east, across Adak and
Atka, models have slowed the eastward progression of the front,
and precipitation is now expected to arrive after temperatures
have climbed above freezing. Thus, snow, if any, will likely be
short-lived and negligible.

Regardless of precipitation, strong southerly winds are forecast
across both the Western and Central Aleutians through tonight.
Gusts to as high as 60 knots will be possible for the Western
Aleutians through the evening hours while after dark the front is
expected to overspread the Central Aleutians with winds gusting to
50 knots. The front will finally reach the Eastern Aleutians and
Pribilofs in a weakened state late Thursday into friday.
Regardless, winds gusting to 30 knots will still be possible for
towns of Dutch Harbor, Saint Paul, and Cold Bay.

Much uncertainty arises by day three in regard to what the
western Bering upper low finally decides to do. Models suggest
that a North Pacific low will pivot around the eastern periphery
of the western Bering low and track into the Alaska Peninsula by
Saturday. The continued presence of the western Bering low and the
additional arrival of a North Pacific low will likely continue
the unsettled weather pattern for the entire region with
widespread scattered showers and low stratus.

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

The long-term pattern has remained relatively consistent over the
last few days. High pressure ridging over Canada extends into
eastern Alaska, with longwave troughing over the Bering Sea,
spreading into portions of western Alaska and the Gulf of Alaska.
There will be several shortwaves rounding the base of the trough,
moving over the Aleutian Chain and southern Alaska Peninsula, as
well as across the Bering Sea. There is a strong zonal jet that is
forcing most of the developing North Pacific systems towards the
continental West Coast, with milder, weaker systems moving towards
the Gulf. The coastal regions will likely see periods of
precipitation, including the north Gulf coast, Kodiak Island, and
the Aleutian Chain, while the mainland regions will remain under
the influence of the upper-level ridge. Upper-level ridging will
get shunted off to the north as the trough pushes towards the
north Gulf coast, gradually weakening over time.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning: 178, 411
		 Gale Warning: 172-177, 412, 413
 		 Heavy Freezing Spray: 185
FIRE WEATHER...NONE.

&&

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