Blizzard in Alaska, February 29, 2020

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
452 PM AKST Sat Feb 29 2020

.ANALYSIS AND UPPER LEVELS...

A deep 962 mb low over the Bering is moving northeastward. A
trough-axis associated with this low extends southwestward
through the western Aleutians and into the North Pacific. The
jet-stream currently extends northeastward from the sub-tropical
Pacific into Southcentral Alaska. Difluent flow in the upper
levels is occurring over Southwest Alaska as this area is located
in the left-exit region of the jet. High pressure ridging
currently extends northward from the eastern Pacific into the
eastern Gulf.

At the surface, a 1022 mb high is located over the central AlCan
border. Radar imagery shows snow moving into the Kuskokwim Delta
and Bristol Bay.

&&

.MODEL DISCUSSION...

Models are in generally good agreement through the middle of next
week and then fair agreement towards the end of the week with the
overall synoptic pattern. Due to the good agreement, the forecast
confidence is above normal. Higher resolution models were favored
for local effects as these models resolve mesoscale effects best.

&&

.AVIATION...
PANC...Ceilings and visibilities will lower in the MVFR to IFR
range this evening with the onset of snow. Ceiling and
visibilities may improve briefly overnight before diminishing
again in snow Sunday. LLWS will also develop by early evening with
strong southeast winds developing above northerly surface winds.
LLWS should end early Sunday morning.

&&

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

Snow is currently developing from south to north across the
region. It will gradually increase in intensity through the
evening. For the Anchorage area, approximately 1 to 2 inches are
likely this evening. A brief lull is expected early Sunday morning,
before the surface and upper level flow pattern becomes
unidirectionally southwest. This will allow the snow to persist
through early Monday morning. There is currently good consensus
among the models indicating approximately 7 inches of total
accumulation. Blowing snow is possible along the Hillside this
evening, though visibilities are not expected to be reduced for
extended periods. Scattered snow showers remain possible in a
cold, northerly flow through Tuesday as the associated low
retrogrades near Prince William Sound.

A Winter Weather Advisory will begin this evening for the Susitna
Valley. Upslope flow will enhance snowfall totals, with over a
foot possible in some areas through Monday morning, particularly
between Talkeetna and Chulitna. Winds will remain generally light.
Light snow is likely to persist through Monday in the
aforementioned cold, northerly flow.

Blowing snow remains likely across the western Kenai Peninsula as
well as the Portage Valley, eastern Turnagain Arm and Turnagain
Pass. These will continue through midnight and 6 AM respectively.
Snowfall totals will be similar to Anchorage. Higher-elevated
areas near Homer may briefly see blowing snow as well as a mesolow
tracks near Kachemak Bay on Sunday afternoon.

Areas along northeastern Prince William Sound (Valdez/Cordova)
will likewise see a significant amount of snow, with 20 or more
inches expected through Monday. Periods of blowing snow are
possible through Thompson Pass this evening through Sunday
morning.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 2)...

A strong low continues to move toward the Southwest coast. The
leading edge of the front currently moving inland has brought
gusty winds and snowfall to the Kuskokwim Delta and Bristol Bay
area, and rain to the southern Alaska Peninsula. The Winter
Weather Advisory initially in place for the Kuskokwim Delta has
been upgraded to a Blizzard Warning due to intensifying winds and
low visibility, especially along the coast. Precipitation type has
been somewhat of a challenge with this forecast, especially
across the interior areas of Bristol Bay, as there is warm
southerly flow aloft that may allow for a rain/snow mix or
possibly freezing rain at times. As the low nears the coast
by early Sunday morning, colder air will wrap around the backside
of the low allowing any lingering rain or rain/snow mix to change
over to snow. Gusty southwesterly flow will continue along the
Bristol Bay coast through Sunday night before tapering off for
Monday. As the low moves inland, northerly flow will return across
Southwest allowing cold Arctic air to move in over the region for
Monday.

&&

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

A strong low centered near the Pribilofs continues to move to the
northeast. Observations confirm a large swath of storm force winds
over the central Aleutians. On the south side of this low, moist
southerly flow has allowed for rain along the Chain, however
colder air on the north side of the low has brought gusty winds,
snowfall, and reduced visibility to the Pribilof Islands at times.
As the low center moves into the eastern Bering, storm force winds
will also progress eastward along the Chain, with both the Bering
side and Pacific side seeing strong gusty winds through Sunday. On
the backside of this low, cold northerly flow will return to the
Bering by Sunday night. Farther west, a second, weaker, low spins
up Sunday night over the Rat Islands. This low could potentially
produce gale force winds as it gradually moves south of the
Aleutian Chain for Monday.

&&

.MARINE (Days 3 through 5)...

A low in the Gulf will exit to the east and weaken Tue through
Wed. Expect enhanced NW winds over the Barren Islands, likely to
gale force with broader areas hitting small craft advisory level
elsewhere in the Gulf. Meanwhile, looking out west, steady
anticyclonic flow will enhance gap winds south of the AKPEN. The
next low will approach from the eastern Pacific Wed to Thu,
potentially bringing gales and heavier seas to the Bering Sea by
Thu.

&&

.LONG TERM FORECAST (Days 4 through 7)...

A low in the Gulf of AK will pull east and weaken Tue into Wed,
leading to cold, dry conditions and generally offshore flow
inland. Meanwhile, a ridge will build over the Bering Sea and dry
weather will persist over the Southwest Mainland through Thu. A
low will approach the western Aleutians Wed into Thu, and track
into the eastern Bering by Fri. The Arctic high looks to weaken
and recede towards the Alcan later in the week, indicating a trend
towards warmer conditions over Southern Alaska. A sacrificial
front associated with the Bering low will push into the Southwest
Mainland Fri to Sat; precipitation doesn't look to amount to much
over the mainland. A more robust system will approach the Aleutians
Fri to Sat, bringing a better chance for precipitation across the
mainland Sat or Sun.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 155.
         Winter Weather Advisory 121 125 145 152 161.
MARINE...Storm Warning 150 155 160 165 170 171 172 173 174 175 176 180.
   	Gale Warning 119 120 125 130 131 132 139 141 177 179 181 185.
    Heavy Freezing Spray Warning 139 179 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ED
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...MM

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
455 PM AKST Sat Feb 29 2020

AKZ101-010300-
Anchorage-
Including the cities of Anchorage, Eagle River, Indian,
and Eklutna
455 PM AKST Sat Feb 29 2020

...SNOWFALL ACROSS THE ANCHORAGE BOWL THROUGH SUNDAY NIGHT...

Snow is expected to develop early this evening across the Anchorage
Bowl and continue through Sunday. Total snowfall of 5 to 8 inches
is expected across the Anchorage Bowl from this afternoon through
Sunday evening.

Please visit http://weather.gov/afc for your local forecast.