NWS Anchorage, AK wrote its last area forecast discussion before the first event at Feb 5, 4:59 AM AKST, 10 hours 20 minutes earlier.
Area forecast discussion, Feb 5, 4:59 AM AKST, 10 hours 20 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
459 AM AKST Sat Feb 5 2022
.ANALYSIS AND UPPER LEVELS...
In the upper levels a shortwave trough is moving across the Kenai
Peninsula with areas of light snow reported by observations and
radar. The radar shows the heaviest band of snow across Cook Inlet
and the western Kenai Peninsula extending into Anchorage and the
MATSU valleys. Farther east this wave is pushing rain and snow
onshore across Prince William Sound with snow reported inland and
rain or a rain/snow mix near coastal areas. A surface low is
moving onshore across Bristol Bay with a rain/snow mix reported at
King Salmon and light snow across much of Bristol Bay as seen
slowly moving north on radar. Fairly quiet across the Bering with
a weakening cold front extending across the northern Bering with
light snow occurring near the front. Across the western Aleutians
a persistent low continues to spin west of Attu Island and will
finally move towards Kamchatka later today. Last but not least a
strong low pressure system is seen on satellite over the North
Pacific and will enter the Gulf later today, this will be the next
major weather producer for parts of Southcentral.
&&
.MODEL DISCUSSION...
Model continue to struggle with the track of the next low pressure
system moving into the Gulf Saturday and Sunday. Currently GFS is
the outlier with a more westerly track moving the low to near
Middleton Island and near Prince William Sound by Sunday morning.
All the other model solutions take a more easterly track moving
the low east of Middleton Island. The biggest forecast challenge
is where snow will fall. If we get a more westward track than
western Prince William Sound and the Anchorage area will see
snow. Otherwise very little if any snow with the eastward track
for these same areas. Finally, towards the end of day three
models are in good agreement as well as run to run consistency
with an upper level shortwave moving across Southwest Alaska
towards Southcentral which will bring a good chance of snow across
Anchorage and the MATSU valleys late Sunday into early Monday
morning.
&&
.AVIATION...
PANC...VFR conditions with temporary MVFR to possibly IFR
conditions as a band of light snow moves across the airfield this
morning. The snow should wind down by around 9 am. Otherwise
expect light northerly winds through the TAF period.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Monday night)...
A short-wave trough lifting northward across Southcentral will
exit northward during the morning hours. Snow will end most places
early this morning, but will linger across the Susitna Valley
through at least midday. Attention then shifts to a storm system
moving out of the Pacific. There is favorable upper level support
for a deepening cyclone in between two jet streaks. However, the
jet support will quickly shift north and east, passing the low by.
Also, one of two short-wave troughs aloft will drive toward
Southeast Alaska. As a result, expect little additional deepening
of the surface low as it arrives in the Gulf this afternoon.
Expect an elongated center with multiple actual lows as new lows
form out ahead of the parent low. This creates some uncertainty in
the track of the low across the Gulf. Continue to favor a track
across the central Gulf to a position south of Cordova on Sunday.
Based on this solution, the bulk of precipitation with this system
will be from eastern Prince William Sound (Cordova and Valdez
areas) northward across the Copper River Basin. Expect little
precipitation for the eastern Kenai Peninsula/Western Prince
William Sound. If the low tracks a little further west, this
could change. The airmass is warm enough for rain along the Gulf
coast and Kodiak Island. Thus, this looks like a rain event for
Cordova, perhaps mixed with snow at times. Valdez and the Copper
River Basin can expect all snow. With offshore flow ahead of the
low this afternoon through tonight, precipitation will initially
be light. However, precipitation will intensify Sunday as the
surface low and upper level short-wave trough arrive.
Meanwhile, a weak short-wave over Southwest Alaska on Saturday
night will approach Southcentral on Sunday, then traverse the
region Sunday night. Cold air advection will accompany the trough.
and help produce areas of light snow. Right now, this looks most
favorable from Anchorage to the Mat-Su, with light accumulation
likely. Following this, an Arctic trough will dig southward across
western Alaska and the eastern Bering Sea. This amplification of
the flow will cause the next storm moving out of the Pacific to
track farther west, likely taking a path near Kodiak Island Monday
and up to the Kenai Peninsula Monday night. While it's too early
to nail down the details of the forecast, this track will bring
warmer air up to Southcentral. Thus, would expect mainly rain
along the Gulf coast and Kenai Peninsula. Stay tuned as we work
out the details of this storm system.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3:
Today through Monday)...
A surface low is continuing northeastward through inland Bristol
Bay this morning. Precipitation will gradually diminish from south
to north throughout the day. Temperatures will continue to trend
colder across Southwest Alaska for the next few days as arctic air
from an upper trough located over northern Alaska dips south
Saturday night into Sunday. The trough deepens through Monday,
bringing brutally cold temperatures around 20 below for the
Kuskokwim Delta/Valley. Offshore flow with winds increasing over
the Kuskokwim Delta and Bristol through Monday, may result in the
potential for the coldest wind chills to approach 40 below near
the Bethel area. However, the position of the arctic airmass along
with an approaching low pressing towards the AKPen late Monday
could ultimately change exactly how cold the temperatures will
become along with the coinciding wind speeds and resultant wind
chills.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Today through Monday)...
Periods of low stratus, light rain, and snow showers is expected
over the next few days as generally weak flow with multiple
surface lows stall across the Aleutians and over the Bering Sea.
As an arctic airmass drops southwestward from North Alaska
beginning Saturday night into Sunday. Winds will accelerate from
the northeast Sunday through Monday but appear to remain near or
below gale force for now. With the cold temperatures and
increasing winds over the Bering over tonight through Monday,
heavy freezing spray will become more widespread from north to
south, reaching towards the southern Bering by Tuesday morning.
&&
.Marine (Days 3 through 5/Monday through Wednesday)...
Gulf of Alaska: A Prince William Sound low moves inland for late
Monday. Southwest gales along the North Gulf Coast diminish
Monday. Seas to 17 feet, subsiding. Forecast confidence is
uncertain for the low's track through the Gulf. A well developed
North Pacific low moves inland through Prince William Sound late
Tuesday. Widespread high end Southeasterly gales ahead of the
front move into the Northern Gulf. Seas building to 17 feet
through Wednesday. High end Southerly gales with the trailing
front over the Gulf and along the Alaska Peninsula Coast through
Wednesday. Seas building to 24 feet.
Bering Sea: Arctic high pressure moves into the Western Bering
for Wednesday. Forecast confidence is uncertain with the low's
track and development. A well developed North Pacific low swings
into the Eastern Bering by Wednesday. High end Westerly gales move
from the Central Aleutians into Bristol Bay and the Eastern
Bering, becoming Southerly by Wednesday. Seas building to 23 feet
Pacific side of the Central Aleutians, and to 20 feet on the
Bering side, subsiding. Northeast gales develop over the Western
Bering late Tuesday. Seas building to 18 feet on the Pacific side
from the Eastern Aleutians along the Alaska Peninsula through
Wednesday.
&&
.Long Term Discussion (Days 4 through 7: Tuesday through Friday)...
Looking ahead into the extended forecast, the latest operational
model runs are in decent agreement with the synoptic scale
features in the short term, but begin to diverge toward the end of
the period. After a relatively brief break with the active
weather, a series of North Pacific lows will track north of the
Alaska Peninsula/Western Gulf beginning late Monday. These storm
systems will tap into a good moisture fetch, bringing a return of
unsettled conditions for the entire southern state with moderate
to heavy precipitation and gusty winds. Depending on how models
are handling the overall positional differences of these lows,
this pattern will likely persist into the middle to latter part of
next week. Out west, an Arctic low over the western mainland will
bring a surge of colder air across the Bering Sea and Aleutian
Islands. As the low meanders over the open waters, model spread
has increased significantly with the interactions of small to mid
scale embedded systems streaming northward from the Southern
Bering Sea. For now, a cool, showery pattern and windy conditions
will be the theme for these regions as we head into next week.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales...119, 120, 130, 131 351, 352.
Heavy Freezing Spray: 179, 185, 412, 414.
FIRE WEATHER...NONE.
&&
SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...VR
MARINE/LONG TERM...MK/MF