Gale Warning 671, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
548 AM AKDT Tue Oct 29 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Thursday night)...

Key Messages:

* Winter Weather Warnings and Advisories remain in effect for much
  of Southcentral this morning. Moderate to heavy snow continues
  to fall across most of the region this morning, with reports of
  difficult travel conditions along area roadways. Conditions will
  improve through the day for the Kenai Peninsula, Anchorage, and
  the Mat-Su. Snow will linger all the way into Wednesday for the
  Copper River Basin.

* A High Wind Warning has been issued for Kodiak Island for
  northwesterly gusts up to 80 mph this afternoon through early
  this evening.

* The next storm system will make its way into the Gulf of Alaska
  Wednesday night through Thursday. This storm looks much weaker
  than the current one, likely bringing only a few inches of snow
  to Southcentral on Thursday.

A high amplitude trough extends from an upper level low over
Northwest AK southward across Southwest AK and then into the
western Gulf. There are multiple out of phase short-waves within
the long-wave trough. A surface low is strengthening out ahead of
the basal short-wave, which is now taking on a negative tilt. The
low is tracking east-northeast across the central Gulf. Widespread
snow is falling across Southcentral, with rain along the
immediate coastline and a few locations in the interior Kenai
Peninsula.

A heavy band of snow which set up from Kenai/Soldotna to Big Lake
last evening has shifted eastward and extends from around
Sterling on the western Kenai Peninsula up to west Anchorage and
right along Knik Arm. Based on these heavier snow rates (around
1 inch per hour), have extended the Winter Storm Warning for the
Western Kenai Peninsula to include inland areas along the
Sterling Highway corridor. In addition, have upgraded Anchorage
from an Advisory to a Warning. The heaviest snow will be early
this morning. Expect an upper low to develop over the northwest
Gulf by mid morning, leading to a shift in flow and lightening up
of snowfall for the western Kenai, Anchorage, and Mat-Su. The
upper low and trough will then dig southeastward across the Gulf,
slowly pulling the surface low eastward and bringing an end to
snow from west to east this afternoon. Cold air advection will
lead to gusty northerly winds for much of the Mat-Su, west
Anchorage, and the western Kenai along Cook Inlet. This will lead
to some blowing and drifting of snow at ground level. However,
the snow is too wet to loft into the air and cause any significant
reductions in visibility.

The furthest west short-wave will be slow to cross Southcentral,
lingering overhead through tonight before finally exiting on
Wednesday. This will lead to a prolonged period of snow for much
of the Copper River Basin. Have upped snow totals quite a bit
with the latest forecast, especially for the Glenn Highway
corridor west of Glennallen as well as the Richardson Highway
south of Copper Center down to Thompson Pass.

Meanwhile, tight pressure gradients will combine with cold air
advection and a strong upper level jet between the trough and a
high amplitude ridge upstream in the Bering Sea to produce
widespread gale to storm force winds across the Gulf waters
today. Cross-sections of the atmosphere over the western Gulf and
Kodiak Island show a descending tropopause fold crossing through
today, with strong downward motion in the atmosphere. This is
favorable for high winds so have gone ahead and issued a High
Wind Warning for Kodiak Island for gusts up to 80 mph. Some of the
strongest winds will be in the Kodiak City area, with gap flow
also contributing to the strength of the winds.

The upper level ridge over the Bering will build over Southcentral
and the Gulf on Wednesday, but will be short-lived. Strong zonal
flow aloft will drive another trough into the region Wednesday
night through Thursday. At the surface, there is good model
agreement on development of a triple point low and a fast track
across the Gulf. This storm will be much weaker than the current
one and will move through quickly. As a result, expect minor
impacts, with up to a few inches of snow possible for much of
Southcentral.

-SEB

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (This afternoon through Thursday evening)...

A storm-force front continues to push through the western
Aleutians and western Bering this morning. As it progresses
eastward, the front will weaken to gale-force as it reaches the
central Aleutians later this afternoon. However, as the surface
low enters the far western Bering, southwesterly winds to near
storm-force are likely in the southwestern Bering and western
Aleutians again on the southern flank of the storm tonight into
Wednesday.

As a strong low develops in the Gulf of Alaska, strong
northwesterly geostrophic flow and cold air air advection will
generate strong winds near storm-force across the far eastern
Aleutians and Alaska Peninsula through this afternoon and will
gradually diminish thereafter. However, the initial gale-force
front with the Bering Sea low will make it to coastal Southwest by
Wednesday afternoon. Confidence in the evolution of precipitation
type particularly near the southern Bristol Bay coast is low, but
snow is likely to start. A triple point low is then expected to
develop along the front in Bristol Bay and push inland, this would
likely enhance the northerly wind component in areas like
Dillingham, keeping them snow, but bring in warmer air aloft
promoting mixing or even a changeover to rain in areas like King
Salmon and Iliamna. Regardless, the potential for up to a few
inches of snow is becoming increasingly likely for a good portion
of Southwest Alaska Wednesday evening into Thursday, with lower
confidence near the Bristol Bay Coast.

Another developing North Pacific low moves towards the Aleutian
Chain Thursday evening. The storm-force winds associated with this
system area expected to remain in the North Pacific through
Thursday evening. There is still some uncertainty in the exact
track of the low and the western cut-off of precipitation.
widespread moderate rain is looking likely across the eastern
Aleutians Thursday night into Friday. An active weather pattern
will continue to unfold over the next few days.

-ME

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

Forecast guidance continues to carry an active weather pattern
across the Aleutians and Bering Eastward through the forecast
period. A leading upper level wave breaks loose to cross the Gulf
of Alaska, with its associated surface front moving into Southeast
Alaska and dissipating through Saturday night. Most of the active
winds and rainy weather is expected to remain offshore over the
Gulf as the low slips Southeastward. A closed upper low near the
Central Aleutians slips over Bristol Bay spools up a large area of
weather through the first half of the weekend before being
absorbed into the larger Bering low by Sunday. Widespread gale
force winds and heavy rain accompany this low, diminishing North
of the Aleutians and AKPEN for late Saturday. Widespread gale
force winds with areas of storm force gusts remain South of the
Aleutians and AKPEN and around Kodiak Island, diminishing across
the Gulf of Alaska through Monday. Areas of heavier rain are
expected to spread along the Southcentral coasts by Monday.

&&

.AVIATION...

PANC...The heaviest snow and lowest ceiling/vis will be through
around 15Z or so, with snow expected to gradually lighten after
that. There is of course some uncertainty in the details, but
with strengthening northerly winds, confidence is high in steadily
improving conditions through the day, with ceiling/vis reaching
VFR by sometime this afternoon. The gusty winds could lead to
blowing and drifting along the ground, but the snow should be wet
enough to prevent lofting of the snow. The gusty northerlies will
die down around or shortly after 12Z Wednesday as high pressure
builds in from the west.

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
232 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0715 AM     Snow             1 NE Anchorage (Huffman 61.12N 149.79W
10/29/2024  M4.0 Inch        Anchorage          AK   Public

            Social media report near the zoo. Tiny
            flakes were still falling at the time of
            report.

&&

rux

Preliminary Local Storm Report
National Weather Service Anchorage AK
234 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0545 AM     Snow             2 ENE Meadow Lakes      61.63N 149.54W
10/29/2024  M10.6 Inch       Matanuska-Susitna  AK   Public

            Social media report with photo of ruler in
            the snow.

&&

rux

Preliminary Local Storm Report
National Weather Service Anchorage AK
244 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0223 PM     Snow             Soldotna                60.49N 151.06W
10/29/2024  M11.0 Inch       Kenai Peninsula    AK   Public

            Photo on social media.

&&

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Preliminary Local Storm Report
National Weather Service Anchorage AK
245 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0233 PM     Snow             1 SSW Anchorage (Sand L 61.14N 149.96W
10/29/2024  M10.4 Inch       Anchorage          AK   Public

            Photo on social media.

&&

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Preliminary Local Storm Report
National Weather Service Anchorage AK
251 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0235 PM     Snow             2 SSE Houston           61.60N 149.76W
10/29/2024  U12.0 Inch       Matanuska-Susitna  AK   Public

            Social media report.

&&

rux

Preliminary Local Storm Report
National Weather Service Anchorage AK
304 PM AKDT Tue Oct 29 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     Snow             1 N Eagle River         61.33N 149.56W
10/29/2024  M5.1 Inch        Anchorage          AK   Public

&&

rux