Small Craft Advisory 37, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 PM AKST Tue Jan 10 2023

.ANALYSIS AND UPPER LEVELS...

The upper level pattern is little-changed from yesterday with the
main jet stream running south of the area and keeping the main
storm track over the western coast of the Continental US. For
Alaska, there is an upper level low near the Bering Strait that
extends southward to the Aleutians with a secondary trough
extending over Bristol Bay and Kodiak. This secondary trough is
moving slowly northward and bringing rain and snow to the north
Gulf coast and Prince William Sound regions though there is enough
downsloping off the Kenai and Chugach Mountains to keep most of
the lee sides of these mountains dry.

A surface low is in Bristol Bay and is the remnant of the one
that crossed through the western Gulf Sunday night. A sharp
temperature gradient can be seen between the warmer Bristol Bay
region in the 30s and much colder Kuskokwim Delta which is in the
lower teens and still has a stiff northerly breeze. The central
Aleutians remain cold enough for snow showers but they are less
widespread than yesterday. Southwest of Attu the large cloud
shield of the next low can be seen on satellite. This is the front
that will bring the storm-force winds to the western Aleutians
tomorrow.

&&

.MODEL DISCUSSION...

Models remain in good synoptic agreement into the weekend, which
is an improvement from even yesterday when there was great amount
of disparity in solutions over the Aleutians for this weekend.
High resolution models continue to indicate higher probabilities
for light snowfall in the northern Cook Inlet region overnight
tonight while the larger-scale models are not so enthusiastic.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through this
evening. Some light snow may develop after midnight (9Z) and bring
in marginal conditions. After the snow ends in the 18Z time frame
tomorrow morning, the MVFR ceilings may persist for a few more
hours and then lift in the afternoon.

&&

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

A weakening front will slowly move north and east, bringing snow
accumulations along the Kenai Mountains and Turnagain Arm and into
the eastern Chugach on Wednesday. Periods of light snow will
continue over the Anchorage Bowl before tapering off tonight in
response to weak synoptic forcing moving the area. Otherwise, the
rest of the Southcentral mainland remains relatively dry due to
downsloping easterly flow. An upper level shortwave meanwhile
tracks northward across the Gulf from this evening to Wednesday.
Another round of precipitation is expected to spread across the
eastern Kenai Peninsula, with the heaviest along Prince William
Sound overnight tonight.

Precipitation type remains snow throughout the period for most
elevated areas, with rain likely for the low-lying regions. As
the shortwave moves into Southcentral, period of light snow is
expected farther inland for the western Kenai Peninsula, Anchorage
Bowl, and the Mat-Su Valleys during early Wednesday. Snowfall
amounts will be up to an inch. A ridge of high pressure builds
across the mainland from Thursday to Friday for drier conditions,
while a wet pattern persists for the coastal areas as a trough
stays over the southern Gulf.

&&

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

A weakening low pressure system over Bristol Bay will continue to
promote unsettled conditions across Southwest Alaska this
evening. The low pressure system is expected to move north out of
the region overnight tonight, however several minor shortwaves
passing through will maintain the chance for showers across
Southwest Wednesday. Following the exit of the low Wednesday
evening, weak ridging will begin to build, advertising a calmer,
drier pattern for the latter half of the work week. Currently weak
winds across Southwest will provide the chance for areal fog
development later tonight across coastal Southwest, and Wednesday
night primarily in the Kuskokwim Delta/Bethel region. No
significant persistent drop in visibility is expected to accompany
these fog events. Steady offshore flow will develop Thursday.
Temperatures in Southwest are expected to lower Wednesday as the
low exits, however have a slight recovery by Thursday.

&&

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

Slight ridging in the Western Aleutians and a weak trough axis
draped across Central and Eastern Aleutians are creating a prosaic
pattern for the Bering. This will soon be shaken up as a leading
front of an approaching North Pacific low enters the Western
Aleutians late tonight/early Wednesday morning. This front will
initially bring a wave of steady snowfall to the Western/Central
Aleutians. The precipitation will continue for this region,
however a shift to mixed precipitation in the late morning, and
any lingering precipitation shifting to rain by the afternoon. 1-3
inches of snow accumulation is expected for the Western/Central
Aleutians, with the highest amounts currently expected near
Amchitka. This front will have a similar precipitation shift
pattern as it pushes across the Chain, eventually weakening by the
time it reaches Unalaska Thursday afternoon. On the backside of
the front, as the parent low advances northward, showery
conditions are expected to similarly spread eastward from the
Western Aleutians which will persist through the work week.

The front will also bring storm-force winds to the Western
Aleutians as it first moves through. Winds along the front will
diminish slightly to gale-force as it pushes eastward along the
Chain. As the low pushes into the Bering, wind direction may be
favorable for gusts into Cold Bay by early Thursday afternoon,
however this may change as even minor updates to the lows track
may affect the wind direction here. Freezing spray near the
Pribilofs, as well as Heavy Freezing Spray along the northern and
parts of Northeastern Bering, will diminish and retreat northward
as the North Pac low moves in.

.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 177 178.
		 Gale Warning 173-176 411 413.
		 Heavy Freezing Spray 185 414.
FIRE WEATHER...NONE.

&&

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