Gale Warning 153, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
543 AM AKST Sun Feb 4 2024

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

Much warmer temperatures this morning across Southcentral with much
of the region seeing light to moderate snow this morning. The
heavier snowfall is occurring along the far western Kenai as a band
of moderate snow moves north up the inlet. Another large swath of
moderate intensity precipitation is moving north across the northern
Gulf, approaching the Prince William Sound and coastal areas this
morning. Temperatures are still cold enough that precipitation will
move in as snow, but lower elevations along the coast near Cordova
and the Copper River Delta may see a period of rain and/or mix as
temperatures warm this morning. Elsewhere, temperatures will remain
cold enough for all snow but temperatures will moderate some as many
areas bump back up into the above zero teens and 20s. The Copper
River Basin will hold onto their below zero temperatures a bit
longer, but even those readings should greatly improve by this
afternoon.

The current system lifting through the AKPen and Kodiak Island this
morning will continue to lift up across Southcentral through the day
today. Models still have a somewhat compact surface low developing
off the tip of Kodiak Island and moving up the eastern Kenai coast
towards Prince William Sound before dissipating near the Sound
tonight. Surface/buoy obs and radar returns indicate that this low
is starting to organize. Winds have increased down Cook Inlet, and
with moderate snow ongoing from near Anchor Point to north of
Nikiski, areas of snow and blowing snow have reduced visibility. As
such, the Winter Weather Advisory remains in effect for the western
Kenai and the Anchorage Bowl this morning. This band should be the
last big push from this system as the trough lifts up across the
Kenai and inland Southcentral today. Snow will start to wind down
later this morning for the southern Kenai and then gradually end
from south to north up the inlet and into the Mat-Su Valley by late
afternoon/evening. Snow will linger over the eastern Prince William
Sound and the coastal mountains, and the Copper Basin through
tonight.

There will be a brief respite before the next system approaches.
Tomorrow's system will follow a similar track as the parent low
lifts northward across the western and central Aleutians and the
associated frontal boundary lifting up towards the AKPen and Kodiak
Island tomorrow morning. Another round of precipitation will
accompany the front, spreading first across Kodiak Island then north
to the Kenai Peninsula and Cook Inlet. Temperatures should be warm
enough that lower elevations on Kodiak Island may see a brief period
of a rain/snow mix before changing over to rain...same with the
southern end of the Kenai. However, points north should still be
cold enough to remain all snow. Snow will spread north through the
day Monday, but there are a few difference to note that would impact
potential snowfall amounts. Models are again in good agreement with
a surface low developing near the Barren Islands, but with this next
system, models are also hinting at midlevel low developing. This
would allow for increasing easterly to southeasterly flow over the
northern Gulf resulting in more of a downsloping component for the
western Kenai and Anchorage Bowl. Several hi-res models are hinting
at a prominent downslope hole developing until late Monday. The
eastern Kenai and western Prince William Sound will see the bulk of
the precipitation, but overall amounts will depend on the track of
the low.

- PP

&&

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

Key Points:

* A series of storms moves in through Tuesday, leading to active
  weather and a gradual warming trend.

* High Wind Watches are in effect for the Central and Eastern
  Aleutians from Sunday evening through Monday morning. Wind
  gusts could reach as high as 75 mph.

* The Blizzard Warnings were canceled this morning for Kuskokwim
  Delta and Bristol Bay. However, we are monitoring the potential
  for another round of blowing snow (with visibilities reaching
  1/2 mile or lower) for Nunivak Island and the Kuskokwim Delta
  coast as the next front moves in on Monday.

Discussion:

A northwest-oriented jet stream continues to bring a steady parade
of storms into the Aleutian Islands, Bering Sea, and Southwest
Alaska. The low that brought blizzard conditions to Southwest
Alaska yesterday is currently weakening as it exits towards the
Kamchatka Peninsula. Its front remains draped across Southern
Alaska, though any lingering snow (or rain, for about King Salmon
and southwards) will transition into snow showers as the front
weakens and exits to the north.

The next storm, a strengthening 968 mb low, is already pushing
into the Aleutian Islands this morning. Gusty east to northeast
winds and rain/snow are currently being observed in Adak and Atka.
As the low and its front move northwards into the Bering Sea
through today, cold air will wrap back around the low and bring
strong winds to the Central and Eastern Aleutians. With the High
Wind Watch in effect, the question will be where gusts to 75 mph
can be expected. Unfortunately, not too much clarity was gained
with the overnight forecast package. Models continue to shift
east/west with the location of the core of strongest winds. Where
overnight model runs suggested an eastward shift towards the
Eastern Aleutians (prompting the expansion of the High Wind Watch
to include this area), the latest morning model runs are moving
the strongest winds back west. There's no question that winds will
be strong; high-resolution ensemble members show at least a
70-90% chance that gusts will exceed 60 mph in the Central
Aleutians, and about a 20-60% chance that gusts will exceed 60 mph
in the Eastern Aleutians. In other words, we have moderate to high
confidence in the floor but much lower confidence in the ceiling
for maximum gusts.

The excitement with this 968 mb low won't just be limited to the
Aleutian Islands. As the front moves into Southwest Alaska, there
is a chance that falling snow in combination with cold
temperatures and gusty winds could lead to another product being
issued for blowing snow, especially for Nunivak Island and the
Kuskokwim Delta coast. The timing for this would likely be from
early Monday morning through late Monday afternoon. There's still
a question of whether temperatures will be cool enough and winds
strong enough to support significant visibility reductions, which
we'll continue to examine for this forecast. Further south, winds
look to remain low enough and temperatures warm enough that
blowing snow should be less of a concern.

The parade of storms continues on Monday night as as a moist,
storm force low moves towards the Eastern Aleutians/Alaska
Peninsula. Another, weaker low follows a similar track on Tuesday
night. All this will bring a continued warm-up across the region,
with maximum temperatures reaching into the 30s and 40s by Tuesday
for all but the Kuskokwim Delta and Valley.

-KC

&&

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

A broad upper level low centered over the Bering Sea moves north
into Chukotka on Wednesday. It elongates, extending a trough
across the Alaska Peninsula and into the Gulf. This delivers gale
force winds across the Bering, and snowy weather across Southwest
Alaska through Thursday. Friday morning a North Pacific low south
of Kodiak Island spreads gale force wind northward across the
Gulf, and brings snow to the northern Gulf coast.

&&

.AVIATION...

PANC...

Snow is expected to continue through this morning and early
afternoon, resulting in cloud ceilings and visibilities remaining
IFR to MVFR. Conditions should improve by late this afternoon.

&&