Blizzard in Alaska, March 2 to 3, 2021

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKST Mon Mar 1 2021

.ANALYSIS AND UPPER LEVELS...
The upper level pattern with a large low over the central Bering
Sea and a trough extending out of it into northern mainland Alaska
is producing southwest flow aloft over most of the forecast area
this afternoon. At the surface, the main low is in the central
Bering Sea with another low near Middleton Island and heading
eastward. This second low, and the front associated with it, has
been the main driver of the snow across Southcentral Alaska
today. This track kept the cold air in place and pushed the
moisture over the colder air in that southwest flow, thereby
bringing a region-wide snowfall. The speed of the frontal
movement has kept accumulations under advisory levels for
Southcentral. The low in the central Bering Sea still has some
very strong winds with is as well as cold air so that is the one
which is bringing some Warnings and Advisories to Southwest
Alaska and the Bering Sea regions.

&&

.MODEL DISCUSSION...
Models remain in good synoptic agreement into late in the week.
NAM and GFS are both in very good agreement with the progression
of the Bering Sea low over the next day which will be key for the
warnings over the eastern Bering Sea region.

&&

.AVIATION...
PANC...Snow will end by this evening with improving ceilings and
visibility. Since it will not truly clear out, ceiling heights
should remain in the 3500 to 5000 ft range through Tuesday
afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Thursday afternoon)...

Snow will gradually taper off through this evening across
Southcentral, although scattered snow showers will persist over
the Copper River Basin trough Tuesday afternoon. Skies will
partially clear overnight as offshore northerly flow develops.
This flow will increase Wednesday leading to mostly sunny
conditions and cooler temperatures. Winds through terrain gaps
will be gusty, but not impactful outside of any transportable
blowing snow. These will diminish by Thursday. The next chance
for snow will not be until the end of the week.

&&

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

A broad low in the Bering will continue to drive the weather
across Southwest Alaska this week. As residual moisture continues
to generate snow across the area in the wake of the initial front,
another round of snow and blowing snow is expected across the
Kuskokwim Delta Coast tonight through Tuesday.

In addition, a long westerly fetch across the southern Bering may
bring the potential for elevated water levels along the northern
Bristol Bay coast, particularly in the Togiak area. Confidence
remains low, however given the lack of shorefast ice in this area,
an increase in water levels along the coast is possible during
high tide this evening into Tuesday morning.

As the low center tracks into the eastern Bering, gusty easterly
winds across the Kuskokwim Delta will shift to northerly and
visibility will be limited at times through midday Tuesday.
Conditions are expected to rapidly improve along the northern
coast by Tuesday afternoon as the main low center moves southward
over the Alaska Peninsula. Precipitation will taper from north to
south across Southwest, but gusty northerly winds are expected to
continue. Snow and gusty northerly winds are expected for Bristol
Bay and areas across the Alaska Peninsula as the low center
tracks toward the southeast through Tuesday night. A much colder
airmass will arrive over the Kuskokwim Delta, and will eventually
move southward, reaching the Alaska Peninsula by Wednesday. An
upper level ridge approaches Southwest Wednesday afternoon before
another front over the western Bering tracks eastward, bringing
the next round of weather to Southwest by Thursday.

&&

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

The broad low over the Bering continues to generate active weather.
The low center, currently positioned over the northern Bering
will track southward this evening, passing just to the west of the
Pribilofs. This is one major change to the forecast since
yesterday, as models have shifted the low track slightly.
Beginning tonight, the Pribilofs will eventually see westerly
winds shift to northerly. Gusty conditions combined with snowfall
will limit visibility through the morning hours on Tuesday. The
low center will then move toward the southeast, arriving over the
eastern Bering by midday Tuesday. As the low begins this track, gusty
westerly winds across the eastern Aleutians and Alaska Peninsula will
continue this evening before also shifting to northerly flow
overnight. This pattern is a favorable setup for snowfall, and in
addition to gusty northerly flow, snow is expected for the eastern
Aleutians and southern Alaska Peninsula. The best guess on
amounts right now is about 4 to 6 inches, with locally higher
amounts possible in higher elevations. Expect limited visibility
across eastern Aleutians and AKPEN through much of Tuesday. As
the low departs and continues to move into the Gulf, conditions
will generally improve across the central and eastern Bering late
Tuesday into early Wednesday. Gusty northerly flow will continue
after snowfall ends, and strong northerly gap winds are expected
across the Alaska Peninsula through late Wednesday. Meanwhile over
the western Bering, another front will arrive Wednesday night,
introducing another round of southerly flow as it traverse west to
east across the Chain this week.

&&

.MARINE (Days 3 through 5: Thursday through Saturday)...

Bering: A well developed front moves into Western Alaska for Fri.
Forecast confidence is good. Widespread high end southerly gale
force winds and waves with areas of storm force gusts moves with
the front. Waves building to 20 feet Fri. The associated well
developed low and trailing front move across the Bering from the
West through Fri, and brings widespread high end westerly gale
force winds across the Aleutians/Bering through Sat. Waves
building to 35 feet over the Central Bering subsiding to mid-20s
over the remainder of the area through Sat.

Gulf of Alaska: A low slowly exits the Southern Gulf Fri, with
outflow small craft winds off the Alaska Peninsula from the Barren
Islands to the Shumagin Islands right behind. Models vary, but
confidence is good. A new low and front move across the Gulf
through Sat, bringing widespread southeasterly winds with the
front through Fri. Northwest small craft winds with areas if gale
force gusts follow after frontal passage Sat. Waves building to 12
feet across the Southern Gulf, subsiding Sat.

&&

.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...

Active weather is expected to makes its return to southern Alaska
during the forecast period with the details of each individual
system uncertain at this time. Model guidance keeps a rather
strong Arctic/Siberian upper level low over northeast Russia while
upper level ridging tries to push northward along the Alaska
Peninsula into Southcentral and Southeast Alaska. The storm track
will basically be from the western Bering eastward along the
Aleutian Chain to Kodiak Island and then to somewhere near Prince
William Sound as these ride the eastern periphery of the deep cold
Arctic/Siberian air over northeast Russia. Overall, expect a
milder pattern to ensue for this time period with temperatures
still slightly below normal but closer to the normal values of
where they typically are this time of the year which is near 32
degrees F for Anchorage. This pattern could potentially mean a
snowier regime for Southcentral and in particular across the
Anchorage Bowl. However, many factors have to come together for
Anchorage to get the snow, though, the storm track looks favorable
with model guidance mostly bringing lows near and into Prince
William Sound with details of each uncertain.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 185 195.
		 High Wind Warning 185.
		 Winter Weather Advisory 155 181.
MARINE...Storm Warning 170 171 413 414.
		 Gale Warning 119 120 131 150 155 160 165 173-181 185
					  351 352 411 412.
		 Heavy Freezing Spray Warning 155 160 165 170 179 180
								      185 411 412 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...MK/MV