Gale Warning 141, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
440 PM AKST Sat Feb 11 2023

.ANALYSIS AND UPPER LEVELS...

An upper level long-wave trough dominates most of Alaska and the
Bering Sea, anchored by a broad upper level low over St. Lawrence
Island. Several short-waves are rotating around the broad upper
low, with one primary short-wave trough extending over much of
Southern Alaska and the Gulf of Alaska.

At the surface, broad low pressure is slowly moving east over the
AKPen and Kodiak Island. Analysis also shows a low pressure trough
stretching from the western Gulf into the North Pacific south of
the eastern Aleutians.

Areas of light snow are occurring from Southcentral to Southwest
Alaska where broad low pressure is in place. Light rain is
occurring mainly in the Prince William Sound region with relative
warm onshore flow.

&&

.MODEL DISCUSSION...

Models remain in decent agreement with the synoptic features
through Tuesday. The biggest challenge in the near-term will be
determining the most likely evolution of the surface low moving
into the northern Gulf tonight, and the location and strength of
any enhanced areas along the front associated with that low. Main
impacts with this uncertainty continue to center around marine
winds and timing of heavier precip. Further out, models remain in
decent agreement regarding the general track and strength of a
strong low pressure system expected to move across the Aleutians
on Monday into Tuesday.

&&

.AVIATION...

PANC...Predominantly MVFR vis with 2-4SM in light snow and MVFR-
VFR cigs through the TAF period. CIG/VIS could drop to IFR with
any heavier snow bands snow moving through.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Tuesday)...

An active weather pattern will continue for the next few days
across Southcentral Alaska as a series of lows move across the
region. Radar imagery shows snow moving across the Anchorage Bowl,
Kenai Peninsula, Prince William Sound and the Matanuska Valley
this afternoon. Snow will continue on Sunday as this low lingers
in the northern Gulf near Prince William Sound. The position of
this low will help minimize the downslope forcing across the
Anchorage Bowl and thus keep the chances for snowfall high. Snow
will then taper off across the region Sunday night into Monday.

The other major story will be the strong northwesterly flow and
cold air advection behind this low Sunday through Tuesday. Strong
northwesterly gap flow is expected across the waters encompassing
the western Gulf of Alaska. Heavy freezing spray is expected due
to the cold temperatures in conjunction with these strong winds.
These strong northwesterly winds will gust to hurricane force at
times in the bays and passes due to the localized funneling of
winds. A Blizzard Warning has been issued for Homer for Sunday
afternoon and evening due to these strong winds resulting in
blowing snow that will reduce visibility to one quarter of a mile
or less at times.

&&

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

Cold will persist throughout Southwest Alaska through Monday
night, especially for the Kuskokwim Delta. Wind chills will
generally run 20 to 30 below zero overnight for the Delta with
winds easing tomorrow. However, the lower winds will allow
temperatures to drop lower Sunday night. The one caveat is that
if low clouds and fog develop it would keep temperatures from
being as cold.

The next front will start to impact the Kuskokwim Delta and
Bristol Bay coast late Monday into Monday night. This will
increase winds again for the area. It may also bring in some snow
and blowing snow, but that completely depends on how far north
the front is able to push, and that is a big uncertainty at this
time.

&&

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

Lots of action for the Bearing Sea and Aleutians the next few
days. A strong low will approach the Western Aleutians Sunday and
that will bring in very strong winds to the Central and Western
Aleutians. It will be cold enough for snow as the front approaches
so there may be some periods of heavy snow in strong winds for
Adak late Sunday afternoon and evening. This may cause some
significantly reduced visibility in the snow at times, but as
temperatures will be approaching freezing, visibilities are not
expected to drop to blizzard conditions. It looks like the front
will push through overnight turning the precipitation to rainfall.
Adak could see some strong winds and heavy snow again Monday
night when the cold advection in the northwest winds wrap into
that area.

Dutch Harbor may also see a periods of strong winds and heavy
snow Sunday night, but precipitation there is also expected to
turn to rain by morning.

As the front moves northward, the Pribilof Islands may see another
round of snow and blowing snow on Monday with Blizzard conditions
possible.

&&

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

A highly amplified pattern is expected next week with a series of
strong lows forecast to track across the region. The run to run
continuity with the models is resulting in low forecast
confidence this forecast period. But there are a few things to
glean. The Gulf of Alaska looks active. Out west, a low near
Kamchatka, potentially as deep as 944 mb, pushes a storm force
front into the western and central Aleutians on Wednesday. The
front sweeps to the eastern Aleutians by Thursday. Model uncertainty
amplifies with time. Generally expect a series of short-waves
embedded in the long-wave pattern to traverse the Bering Sea
region. This will result in continued active weather from the
Aleutians to southern Alaska. The overall progressive upper level
flow will maintain a cold enough airmass to support primarily snow
over southern Alaska.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 121.
MARINE...Heavy Freezing Spray Warning 130 131 132 136 137 138 139 141
                                      150 160 165 179 180 185.
         Storm Warning 120 130 131 138 175 176 177 178.
         Gale Warning 119 121 132 136 137 139 141 150 155 170 172 173 174.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...NR
SOUTHCENTRAL ALASKA...ED
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...EZ
LONG TERM...PS