Gale Warning 221, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 PM AKST Wed Mar 1 2023

.ANALYSIS AND UPPER LEVELS...

The jet stream is becoming zonal near the Aleutian Chain then
dipping south of the AKPen into a trough and northeast towards
Southeast Alaska. The jet is supporting a storm force low moving
towards the western Aleutians with a broad ridge across the Bering
with unstable snow showers across the eastern half of the Bering
into the eastern Aleutians and AKPen. A shortwave is diving south
near the Kuskokwim Delta producing gusty winds with light snow and
blowing snow. Gale to storm force winds are driving south across
the eastern Bering, the AKPen, and Kodiak Island. Across the Gulf,
a strong occluded low is moving east across the northern Gulf with
radar showing light snow and flurries across the Kenai Peninsula
and light to moderate snow across eastern Prince William Sound.
This low is also producing strong winds with gusts to 35 knots
near Seward and gusts to 50 knots at Whittier, with gale to storm
force winds across a good portion of the Gulf.

&&

.MODEL DISCUSSION...

Models are in much better agreement through Saturday with the main
forecast challenge in the short term being strong northwesterly
outflow winds from Kodiak Island and along the typical gaps in
Southcentral including Seward, Whittier, and Valdez.

&&

.AVIATION...
PANC...MVFR conditions will improve to VFR this afternoon. A few
snow flurries or brief periods of light snow are possible through
tonight which could bring visibility and ceilings down to MVFR at
times. However, snow accumulations will be less than a half inch
if any does occur.

&&

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

A deep low in the eastern Gulf of Alaska this evening will exit to
Southeast Alaska along with its occluded front by tonight. Thus,
the heaviest snow, ongoing over the Copper River Basin, will
gradually come to an end from west to east, with the exception of
continued upslope flow along the north facing slopes in the
southern periphery of the basin. Further west, snow is already
limited to the western facing slopes of the Chugach Front Range
and Kenai Mountains, aided by northwesterly cold advection. This
is now expected to produce only a few inches of accumulation for
the Anchorage Hillside, with minimal accumulations in the
Anchorage Bowl and surrounding lower elevations. Upslope snow
will gradually taper off through Thursday morning region-wide.

Residual low pressure in the northern Gulf will continue to draw
gusty gap winds out of bays and passes along the north Gulf coast.
This will be the main impact for mainland Southcentral, with the
exception of localized blizzard conditions from gusty westerly
winds resuspending snow in Whittier through the evening. For
Kodiak Island, another round of cold air advection and a
second vigorous upper-level wave moving over the region from the
Alaska Peninsula will lead to a second round of high winds
Wednesday afternoon. A High Wind Warning continues to be in effect
for the potential for 80 mph gusts this evening before winds begin
to diminish overnight. Snow showers embedded in the cold air mass
may intermittently reduce visibility to one half mile in
combination with the high winds.

Drier, colder air works its way across Southcentral and the Gulf
of Alaska, bringing colder temperatures for Thursday and Friday.
As the low in the Gulf weakens on Thursday, its ability to draw
cold air across the Western Alaska/Aleutian Range wanes. Gap
winds diminish somewhat and westerly storm force winds diminish to
gale force over the open waters as a result. This will
be short-lived, however, as winds are expected to increase once
again Thursday night with a renewed push of cold air streaming
south across Southcentral and building high pressure over Interior
Alaska. Winds peak again Friday along the coast, though they are
not expected to reach high wind criteria for Kodiak Island again.
Inland areas see a break from the active weather with relatively
benign, and likely clear, conditions settling in for the end of
the week. By Saturday, a strong upper-level ridge begins to move
in from the west, bringing warmer temperatures and surface high
pressure. This will relax temperature and pressure gradients,
allowing gap winds to diminish.

&&

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

A large upper-level trough continues to swing over the Mainland,
creating an overall amplified pattern across the region. Strong
cold air advection occurring along the backside and base of the
aforementioned trough is denoted by a broad area of popcorn-like,
convective showers stretching across the central and eastern
Bering/Aleutians on Satellite Imagery this afternoon. This strong
cold air advection is producing gusty winds that are accompanied
by snow showers across the Alaska Peninsula. As a result, a Winter
Weather Advisory is in place until later this evening for blowing
snow that will reduce visibilities to one-half mile from Pilot
Point south. Snow and winds will gradually taper off throughout
tonight as the bulk of the energy shifts to the east. A ridge of
high pressure will build in behind the aforementioned trough
creating clearer and colder conditions tonight. Temperatures will
drop to the negative teens across the Kuskokwim Delta and Valley
for Thursday night, which may create a concern for wind chills as
clouds are expected to clear the area. Temperatures will then
begin to warm up into the beginning of the weekend as the flow
becomes more southerly and warmer air is drawn northward into the
region.

&&

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

Strong cold air advection is occurring along the backside and
base of an upper-level trough that is swinging over the Mainland
and causing gusty winds across the region. Accompanying these
winds are snow showers along the eastern Aleutians and Alaska
Peninsula. These gusty winds and snow showers are expected
produce areas of blowing snow that will reduce visibilities down
to one-half mile. As a result, a Winter Weather Advisory is
in effect for blowing snow concerns along the southern Alaska
Peninsula. Winds will taper off through the overnight hours
tonight but light snow is likely to persist through Thursday
morning. Gale force northwesterly winds will gradually decrease
across the eastern Bering tonight as the trough pushes to the
east. The Pacific side of the Alaska Peninsula will experience
some storm force winds along with high- end storm force gusts,
with higher winds expected through bays and passes early tonight
before gradually decreasing through the night. A low located in
the western Bering will have areas of gales and storm force winds
wrapping around it as it tracks southeastward through the Bering
and across the central/eastern Aleutians tonight. Winds and
precipitation will decrease overall for Thursday night as a ridge
of high pressure builds over the Bering. As the flow becomes more
southerly, warmer temperatures will be drawn northward into the
region. However, calmer conditions will be short-lived as a North
Pacific low is expected to track across the western
Bering/Aleutians later this weekend.

&&

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

The key feature for the long term is a building ridge of high
pressure over the mainland. The overall pattern looks to be highly
amplified as the ridge axis aligns over the central mainland and
extends southward over the Gulf. This will introduce a surge of
southerly flow with warmer air and the potential for rain,
particularly across the Aleutians and the western part of the
state (Alaska Peninsula, Southwest). By early next week,
conditions across Southcentral look to remain fairly quiet as the
ridge remains nearly stationary. Meanwhile, the Bering,
Aleutians, and west coast will see active weather as several lows
are steered northward thanks to the blocking ridge. Areas along
the northern Gulf coast may see gusty northerly winds initially
over the weekend, though as the center of the ridge gradually
drifts eastward early next week, these winds should relax as the
pressure gradient weakens. Beyond Monday, there is a lot of
uncertainty regarding to how the ridge interacts with several
upper level waves arriving from the west. While the ridge looks to
be strong and persistent, models are hinting at it breaking down
at some point mid-week, however there is low confidence on the
timing at this point.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 101 141 161 181.
		 Blizzard Warning 125. High Wind Warning 171.
MARINE...Gale 1190 120 125 129 136-139 141 155-165 171 172 174 176
		 Storm 130-132 150 170 173 175 177 178.
FIRE WEATHER...NONE.

&&$$

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...CQ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
LONG TERM...KO

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
242 AM AKST Thu Mar 2 2023

AKZ131-022100-
Northeast Prince William Sound-
Including the cities of Valdez and Thompson Pass
242 AM AKST Thu Mar 2 2023

...STRONG NORTHERLY WINDS FOR THOMPSON PASS TO VALDEZ THURSDAY
MORNING...

Northerly winds 25 to 40 mph with gusts to 55 mph have developed
early this morning and are expected to persist from Thompson Pass
to Valdez through around noon Thursday before slowly diminishing.
Expect areas of drifting and blowing snow in Valdez and along the
Richardson Highway. Although not as strong as this morning, winds
will remain gusty through Friday. A second round of very strong
winds, with gusts to 70 mph, is possible for Thompson Pass to
Valdez late Friday evening through Saturday.

High winds may move loose debris, damage property, and cause
power outages. Travel may be hazardous, especially for high
profile vehicles, and in areas of drifting and blowing snow.

For the latest forecast, please visit www.weather.gov/afc

For the latest road conditions call 5 1 1 or visit
511.alaska.gov.