Small Craft Advisory 77, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 PM AKST Wed Jan 26 2022

.ANALYSIS AND UPPER LEVELS...
Today represents the relative lull in between two weather systems
across Southcentral. The system that moved through yesterday
bringing snow to much of the area moved quickly to the NE courtesy
of a 100+ jet at 300mb (30,000'). A transient ridge of high
pressure and the fresh snow helped to create some patchy fog this
morning across parts of the Mat-Su Valleys. The next system is
already moving quickly from the North Pacific towards the Gulf of
AK. Snow started early this morning for Kodiak Island where
several inches had accumulated by midday. Temperatures there were
hovering right around the freezing mark, so most of the snow was
quite wet and heavy. Snow started across the southern Kenai and
parts of the Copper River Basin early this afternoon as the
occluded front lifted north. The rest of inland population
centers saw dry and cloudy conditions.

Further to the west, a storm-force low moved into the Western
Aleutians overnight and this morning. Gusts in the mid-50 mph
range were observed over Shemya Air Station. This system peaked
this morning with the aid of a 85 kt jet at 300 mb. It is now
weakening as it drifts to the north. The rest of the Bering and
Southwest AK remain quiet under a dominant area of high pressure.

&&

.MODEL DISCUSSION...Models are in great agreement leading to
moderate to high forecast confidence in synoptic features. The
problematic areas of the forecast will be precipitation types at
Kodiak City and snowfall amounts through Friday morning. A
widespread, long duration will move over Southcentral starting
tonight and persisting into Friday morning. As moisture streams in
from the Gulf of AK, a trough of polar air will slide into SW AK.
While this is a favorable set-up for snow for Southcentral, due to
the subtle differences in the evolution of the pieces of energy,
uncertainty remains on exactly where the highest snowfall amounts
will be.

&&

.AVIATION...
PANC...VFR conditions and north winds will persist until snow
starts late tonight. As the snow moves in, expect conditions to
deteriorate in earnest around 13z. Timing could vary by +/- 2
hours. IFR cigs and vis will be likely as snow persists through
much of Thu.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

Light snow will continue tonight and gradually intensify through
the overnight hours. As an inverted trough cycles around the
North Pacific low, precipitation will spread north and west,
beginning with the Copper River Basin and then into Anchorage and
Western Kenai tonight and tomorrow. The inverted trough will
tighten pressure gradients as cold air is drawn south and thermal
gradients will increase as well near the Valdez/Thompson Pass
areas. This will produce blowing snow through Thompson Pass as a
result and a Winter Weather Advisory has been issued. Total snow
accumulations of 6 to 12 inches with winds occasionally gusting to
as high as 35 mph are possible in Thompson Pass. Winds will
generally increase through tonight with light snow beginning to
pick up through the overnight hours as it spreads north and east.
Snow and isolated pockets of blowing snow will be possible for
inland areas located on the western Kenai Peninsula. However, the
combination of winds gusting to 30 mph and falling snow, will
produce the worst conditions near the Cook Inlet. As a result, a
Winter Weather Advisory has been issued for the area. Falling snow
has already started across the Copper River Basin and will
persist into Friday morning. Snow accumulations are expected to be
between 6 to 12 inches. The highest accumulations will generally
be from Glennallen south. Meanwhile, north winds are expected to
increase from Paxson to Isabel Pass midday Thursday. Winds are
expected to gust as high as 35 mph which could reduce visibility
in blowing snow. Therefore, a Winter Weather Advisory has been
issued for this area as well. As with all blowing snow events,
visibility reductions are to be expected, as well as periods of
heavy snow and gusty winds.

Snow will continue to fall in Kodiak this evening then transition
to a rain/ rain snow mix late tonight due to warm air advection
from the Gulf. This pattern may persist with a back and forth
between rain and snow through the end of the week.

&&

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

Areas of low clouds and patchy fog extending across the Lower
Kuskokwim Valley and Kuskokwim Delta will linger through tonight.
By Thursday, an omega blocking pattern will be positioned over the
western Alaska region with the amplified ridge axis over the
eastern Bering Sea. Clear skies and colder conditions will prevail
for the Southwest mainland as the aforementioned ridge shifts
over the state. Daytime temperatures will range anywhere between
the single digits to the teens and overnight lows below zero.
Northeasterly winds will also increase from Thursday to Saturday
in response to a tightening pressure gradient between a North
Pacific low in the Gulf and the eastern Bering high. A combination
of gusty winds and cold temperatures will provide conditions
favorable for wind chills in the -20F to -30F, especially across
the Kuskokwim Delta and Kuskokwim Valley.

As the cold, Arctic airmass descends south of the mainland on
Friday, northwesterly winds will ramp up and funnel through the
gaps and passes along the southern AKPEN. Moisture associated with
the Gulf low may push north of Kodiak Island, bringing a chance
of snow into the Alaska/Aleutian Range. Some of the moisture may
even make its away for interior Bristol Bay and the AKPEN, though
little to no snow accumulations are expected. Snow will taper off
with winds subsiding by Saturday as the low weakens and the
thermal gradient relaxes, leaving benign conditions for the rest
of the weekend.

&&

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

Forecast remains on track with a deep North Pacific low
approaching the Western Bering/Aleutians this evening. The
associated front will bring widespread gales with storm force
gusts, rain/snow mix, and elevated seas above 20 ft into the
northern Bering Sea. With the exception of small craft winds, most
of the active weather will stay west of the Pribilof Islands and
Central Aleutians through Friday morning. Friday afternoon into
Saturday, a second North Pacific low will approach the southern
Bering Sea. Expect another round of gales and rain/snow mix
extending across the same regions. A cold, Arctic airmass moving
over the eastern Bering Sea will provide conditions favorable for
northwesterly winds to funnel through the gaps and passes in the
Eastern Aleutians from Friday through Saturday. This will also
contribute a return of heavy freezing spray for the offshore
marine zones and near the ice edge as well.

&&

.MARINE (Days 3 through 5 - Saturday through Monday)...

Gulf of Alaska:

A weakening low tracks across the Gulf through Monday. Forecast
confidence is good. Gusty Northwest gap winds expected through the
Barren Islands and near Sitkinak for Sunday. Gusty Westerly winds
spread across the Southern Gulf through Monday. An Easterly
Barrier Jet forms along the Alaska Peninsula into the Eastern
Aleutians for Monday.

Bering Sea/Aleutians:

A well developed Central Aleutian low moves to the Central
Kamchatka coast for Monday. Widespread gales from the Pribilofs
West through Monday, with areas of storm force winds near the
Western Aleutians, diminishing Sunday. Seas building to 25 feet
Sunday over the Western Bering, subsiding Monday. Seas on the
Pacific side of the Aleutians to 20 feet, subsiding Sunday.

A North Pacific low approaches the Central Aleutians for Monday.
Forecast confidence is low, due to the low's track and
development. Winds and Sea state are uncertain with this low.

&&

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

A quite interesting pattern is expected as multiple upper-level
shortwave troughs advance through the forecast area for the long
term. Upper-level ridging from the North Pacific transiting from
west to east (eastern Bering through Southcentral) could create a
challenging forecast especially for P-type and snowfall amounts.
Rapid-moving shortwave troughs aloft combined with cold air
advection could bring considerable snowfall amounts across
Southwest and Southcentral. Dry but cooler temperatures could
likely linger over Southcentral, and somewhat rising temperatures
and increased weather activity over Southwest through Wednesday.
Stronger winds and elevated seas are expected over the
Bering/Aleutians, posing stronger gap winds for much of the
Aleutian Chain through Wed.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 121 131 141.
MARINE...Gale Warning 119 120 130 132 138 139 150 155 175-178 180
					  185 411-413.
		 Heavy Freezing Spray Warning 139 150 160 165 179 185 412.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...NS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MF
MARINE/LONG TERM...MK/CB