High Wind Watch 8, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
441 AM AKST Thu Mar 2 2023

.ANALYSIS AND UPPER LEVELS...

A longwave trough remains draped over interior Alaska with its
axis oriented along the ALCAN border. Helping the trough push
gradually eastward is the continued presence of a vigorous
shortwave trough now over the eastern Gulf and pushing into
Juneau. Cold temperatures aloft have contributed to instability
over the warmer Gulf waters and numerous convective showers are
ongoing. On the backside of the shortwave and upstream of the
longwave trough, strong cold air advection continues to spill
across Southwest Alaska and into the western Gulf waters. Inland
temperatures across Southwest remain cold with morning lows in the
single digits and below for much of the region. An enhanced
pressure gradient has developed from the AKPEN into Kodiak Island
with westerly winds gusting to 30+ knots. Kodiak City has observed
gusts to 50+ knots through the early morning hours. Across the
Bering a persistent upper low has now overspread the Pribilof
Islands. The presence of the low will maintain gale to storm force
westerly winds over the southern Bering and the Aleutians through
the morning hours. Snow along a preceding front stretches from
near Saint Paul, southeastward, to Port Heiden with areas of light
snow showers. However, snow is expected to gradually taper off
through midday.

Further east, snow over Southcentral has largely diminished and a
pattern change is starting to commence. With the eastward shift
in the upper trough over Southcentral, northerly outflow winds
have developed through the gaps and passes. Valdez has experienced
winds gusting from 30 to 50 knots this morning. The orientation
of the pressure gradient has also aligned favorably over Seward,
with northerly winds gusting to around 40 knots. While snow is
gradually coming to an end today, northerly outflow winds will be
common over the coming days.

&&

.MODEL DISCUSSION...

Models remain in good agreement over both Southwest and
Southcentral Alaska in the short term. The greatest uncertainty
exists across the Bering on Friday on Saturday. The forecast
challenge will entail how a Kamchatka low lifting across the
western Bering and a North Pacific low tracking into the Western
and Central Aleutians will interact with each other. Models, begin
to diverge over the weekend with subtle differences in strength
and placement of the North Pacific low over the Aleutians and
western Bering. Over Southcentral, and now that a longwave trough
is finally sliding east of the region, models are in far better
agreement with a weaker and nearly stationary area of low pressure
to hug the coast just east of the Copper River Delta through
Saturday.

&&

.AVIATION...
PANC...VFR conditions to prevail into Friday. Anchorage is
expected to remain situated between a weak low over the northeast
Gulf and increasing high pressure over Southwest Alaska over the
coming days. Which will lend itself to dry conditions and
generally light northerly winds at or below 10 knots through
tonight.

&&

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

Low pressure stalled near Yakutat, combined with a deep polar
airmass advecting over the region from the interior, is resulting
in gusty gap winds through bays and passes along the Southcentral
coast. Winds are expected to relax slightly through the day from
their peak this morning, but will likely increase again for Friday
as the aforementioned low moves south and an upper-level wave
dropping south from the interior reinforces the cold air
advection. These winds will increase through the day Friday with
strong gusts, especially through north-south oriented gaps,
peaking late Friday night through the first half of Saturday, as
the surface ridge over the interior strengthens and tightens the
pressure gradient between it and the Gulf low.

Winds across Kodiak and the western Gulf will also begin to
diminish this morning from their peak overnight. Again, winds will
remain gusty as the colder air filters in from mainland Alaska.

Areas of drifting and blowing snow will continue for locations
experiencing strong winds, especially for Portage Valley and
Whittier, Seward, and Valdez.

In addition to the persistent winds, temperatures will also fall
well below normal through the first half of the weekend as drier
and colder air moves in. By Sunday, 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)...

Snow and winds have tapered off across most of the Southwest
Mainland, with some residual unsettled weather lingering along the
eastern-most portions and along the Alaska Peninsula that should
wind down through this morning. Cold air advection pulls out of
the north today, dropping the overnight temperatures 10 to 20
below, with wind chills dropping into the negative 30's across
the inland areas. Additionally, conditions are expected to be
mostly dry as we approach the weekend.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

A swath of cold air drifting across the Bering sea will allow for
continued gusty winds portions of the southern Bering Sea,
including an area of storm force winds just north of the
Central/Eastern Aleutians today. Precipitation across the Eastern
Aleutians and southern Alaska Peninsula will persist into the
early afternoon and taper off into the evening hours. The edge of
a Kamchatka front will hit the Western Aleutians this afternoon,
but then will track across the northern Bering, avoiding the rest
of the Chain and the Pribilof Islands. A third system pushes out
of the North Pacific and over the Central Aleutians on Friday
bringing another round of precipitation and winds to the area.

&&

.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...NONE.
MARINE...Storm: 130-132 170 173 352 413.
         Gale: 120 127 136-139 150 155 171 172 174-178 185 351 411
               412 414.
         Heavy Freezing Spray: 121 129 130 136-139 141 150 160 165
                               180 185 414.
FIRE WEATHER...NONE.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
150 PM AKST THU MAR 2 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0609 PM     SNOW             BUTTE                   61.53N 149.01W
03/01/2023  M0.7 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

0554 AM     SNOW             BUTTE                   61.53N 149.01W
03/02/2023  M0.6 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

0745 AM     SNOW             EAST ANCHORAGE          61.23N 149.44W
03/02/2023  M6.8 INCH        ANCHORAGE          AK   PUBLIC

0857 AM     SNOW             EAGLE RIVER             61.31N 149.48W
03/02/2023  M1.1 INCH        ANCHORAGE          AK   PUBLIC

&&