Gale Warning 747, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
532 PM AKDT Mon Oct 28 2024

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

Key Messages:

* A major snowstorm is starting to impact a large portions of
  Southcentral Alaska today and will continue through Tuesday.
  Several Winter Weather Advisories and Winter Storm Warnings have
  been issued. A Blizzard Warning will go into effect Tuesday
  morning for Thompson Pass.

* Travel along area roadways will become increasingly hazardous
  tonight through Tuesday morning as snow intensity increases.

* Gale Warnings and Storm warnings have been issued for much of the
  Gulf coastal waters. Kodiak City will see some of the strongest
  winds, with gusts possibly reaching as high as 70 mph late tonight
  through Tuesday.

Discussion:

The much anticipated winter storm has finally arrived with light
snow starting early this morning over the Cook Inlet and eastern
Kenai Peninsula and quickly spread northward through the morning
hours as the initial wave and associated front moved through. Light
snow has continued into this afternoon, but is expected to start
picking up by this evening as the primary trough begins to lift
northwards. Rain and mixed precipitation have remained over inland
valleys of the Kenai Peninsula while the western and far southern
Kenai coastal areas have remained mostly rain as temperatures have
remained in the mid 30s to lower 40s. For the most part temperatures
along the Cook Inlet up through the Mat-Su Valley have remained at
or below freezing, thus limited snow from transitioning to rain or a
mix. As such, several inches of snowfall has already accumulated
along the Sterling Highway from about Ninilchik to Sterling as of
early afternoon which led to bumping up snowfall totals a bit along
the warned area. Snow still looks to increase later tonight through
Tuesday morning for most areas within an advisory or warning as the
upper level trough begins to pivot and lift off to the northeast.

Overall, the forecast still looks to be on track with some minor
shifts in some of the key features. The primary deformation zone
looks to set up over the far western Gulf and eastern Kenai
Peninsula, however, temperatures should remain warm enough in the
lower elevations to remain mostly rain. A secondary deformation band
will set up along the Cook Inlet extending from near Homer to Kenai
and north towards Willow. Several hi-res models have wavered this
band westward and then back to the east per the latest model run, so
while the official forecast highlights the area most likely to see
heavier snow set-up, any shift (however slight) will impact overall
snow totals. For now, have kept current Winter Weather Advisories
and Warnings as is. Eventually, the heavier precipitation will start
to shift east before gradually winding down over western portions of
Southcentral tomorrow afternoon.

By late tonight, the upper level flow will become highly amplified,
with the deep low in the Gulf, a ridge upstream in the central
Bering Sea, and another deep low upstream of that. Low level cold
air advection along with a very strong jet coming across the eastern
Bering and Alaska Peninsula will lead to very strong winds across
Kodiak Island and the western Gulf coastal waters tonight through
Tuesday. For now, have capped winds at 70 mph for Kodiak City (just
below high wind warning thresholds), though will continue to
evaluate this as confidence increases in the depth and track of the
Gulf low.

The low and upper trough will be slow to exit, with snow likely
lingering in the Copper River Basin through about midday Wednesday.
Gap winds along the coast will also persist through Wednesday
morning before lightening up Wednesday afternoon. It looks like
there will be just a brief break in the whether before another
trough and developing low moves into the region on Thursday.

- PP/SEB

&&

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

The back edge of precipitation continues to push through the
Alaska Peninsula, interior Bristol Bay, and into the Alaska Range
this afternoon. Scattered rain and snow showers will continue
particularly across the Kuskokwim Delta throughout the day today.
These showers will also be more convective in nature as cold air
works in behind the system.

Attention then turns to a storm-force front that will impact the
western Aleutians and western Bering late Monday night into
Tuesday morning. Hurricane-force gusts are possible with this
system. As it progresses eastward, the front will weaken to gale-
force as it reaches the central Aleutians on Tuesday. However, as
the surface low enters the far western Bering, southwesterly
storm-force winds are likely in the western Bering and western
Aleutians again on the southern flank of the storm Tuesday night
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 tonight into Tuesday morning and
will gradually diminish throughout the day Tuesday. However, the
initial gale-force front with the Bering Sea low will make it to
coastal Southwest by Wednesday afternoon. Confidence in
precipitation type is low, a rain/snow mix to start is possible
before going over to rain at the coast, with more in the way of
snow inland where cold air hangs on longer. As with the event last
night into early this morning, there is freezing rain potential
across Bristol Bay again with this system. The best chance for
freezing rain, at this point, would across Togiak and Dillingham
be Regardless, there is potential for up to a few inches of snow
again for a good portion of Southwest Alaska Wednesday evening
into Thursday.

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. Stay tuned to the forecast
as the active weather pattern continues to unfold over the next
few days.

&&

.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...IFR to LIFR ceilings and vis are expected to persist
through Tuesday morning. Light to moderate snow will also
continue through around noon tomorrow before tapering off. A band
of moderate to heavy snow is still expected to develop over
northern Cook Inlet late tonight, just west of the terminal. If
this band sets up just a tiny bit further east, that would put
the terminal in the heaviest snow (rates of 1" per hour or more)
while if the band sets up slightly further west then snow will be
lighter and ceiling/vis higher. Ultimately, the band will shift
eastward over Anchorage through early Tuesday morning, so there
will be a period of heavier snow. Significant improvement is not
expected until 20Z or later on Tuesday. Northerly winds will also
increase early Tuesday morning. Gusts around 25 kt are likely,
leading to the potential for drifting snow at the terminal.

&&

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Preliminary Local Storm Report
National Weather Service Anchorage AK
1101 PM AKDT Mon Oct 28 2024

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

1044 PM     Snow             Meadow Lakes            61.54N 149.65W
10/28/2024  M4.5 Inch        Matanuska-Susitna  AK   Public

&&

Preliminary Local Storm Report
National Weather Service Anchorage AK
1102 PM AKDT Mon Oct 28 2024

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

1033 PM     Snow             Big Lake                61.52N 149.96W
10/28/2024  M4.5 Inch        Matanuska-Susitna  AK   Public

&&