Gale Warning 729, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
631 PM AKDT Tue Oct 22 2024

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

The upper-level shortwave and surface cold front responsible for
yesterday's widespread wintry precipitation and strong southerly
winds have moved east over the Canadian Arctic. Multiple, weaker
shortwaves upstream will continue to move west to east through
Thursday as the entire broad, longwave trough settles overhead.
The result will be persistent snow showers over the higher
elevations as a colder, westerly flow develops aloft.

At the surface, a slow-moving surface low over the North Slope
will keep southerly winds gusty through this evening, aided in
part by colder, more unstable air moving over Southcentral behind
the aforementioned front. As colder air arrives, on the
developing westerly flow aloft, winds will diminish across Cook
Inlet but increase for Whittier, Seward, and other gaps along the
Southcentral coast.

A band of light snow or flurries may also develop later tonight
across the Northern Susitna Valley and move southeast through
early morning Wednesday as a shortwave moves through the region.
Light snow accumulations may develop northeast of Palmer toward
Eureka through Wednesday morning, as well as along the Richardson
Highway Wednesday morning. This feature may also produce a few
flurries for lower elevations from Anchorage north and east, with
some lingering and potentially accumulating snow for higher
elevations.

The snow shower activity will likely diminish by Wednesday
afternoon for all locations with the exception of the central
Chugach and Wrangell Mountains. The next low arrives to the
western Gulf from the eastern Bering later Thursday afternoon.
Where Kodiak was being downsloped by westerly winds, a front will
shift the pattern completely, bringing rain and southeast winds
to the Island for Thursday through Friday. The front lifts north
later on Thursday, spreading precipitation across the northern
Gulf coast and Prince William Sound. The surface low and front
look to remain far enough south to keep most of the precipitation
closer to the Gulf/Prince William Sound coastlines with northerly
offshore flow for much of Southcentral.

-TM

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (TODAY THROUGH THURSDAY...)

An active pattern across the Bering and Southwest Alaska will
continue through the end of the week. A low pressure system
responsible for strong onshore winds and coastal flooding across
the Kuskokwim Delta is departing the region. Winds will gradually
diminish through the evening hours and the threat for additional
flooding or coastal erosion has subsided. Temperatures across the
board have warmed to above freezing this afternoon and in the
upper 30s/mid 40s. Southwest temperatures will fall to at or below
freezing tonight with Bering locations remaining in the low 40s.

The next low develops and moves from the southern Bering into the
AKPEN on Wednesday. This will see light snow chances for coastal
regions of the Kuskokwim Delta and higher elevations of Greater
Bristol Bay through the morning hours. Measurable accumulations
are not expected at sea-level. More importantly, strong cold air
advection on the backside of the low will promote gusty northerly
winds from the Pribilof Islands down into the Eastern Aleutians
and Alaska Peninsula. Gales on the order of 40-45 mph will be
common with storm force winds of 55-65 mph likely into Unimak Pass
as well as through bays and passes. The low itself is only
forecast to deepen down to around 998 mb as it skirts across the
Alaska Peninsula, so hurricane force wind gusts are not
anticipated at this time. Scattered showers with a mix of rain and
snow will be possible as the cold air mass spills south of the
Eastern Aleutians. Precipitation chances will be more limited for
coastal Southwest. A quick shot of southwest flow will keep most
precipitation all rain into Bristol Bay.

Finally, a new low is forecast to sweep across the western Bering
on Friday, which will attempt to supplant subfreezing
temperatures with a warmer airmass.

-BL

&&

.LONG TERM FORECAST (FRIDAY TO NEXT TUESDAY)...

A deepening low in Bristol Bay Thursday moves over the AKPen and
into the North Pacific by Friday morning.  During its
southeastward progression, southwest winds and increasing wave
heights are likely along the northern AKPen and portions of the
Southwest AK coastlines. After it crosses into the North Pacific
Ocean, northerly storm force winds through the Central and
Eastern Aleutians are likely through Friday afternoon. Elsewhere,
high pressure in the North Pacific south of Adak will progress
southeastward Thursday as a front from a Kamchatka Low moves
through the Aleutians Saturday reaching the Southwest coastline
early next week. A second low begins to move through the Bering
Sea next Monday.

A low crossing into the North Pacific deepens as it progresses
into the Gulf of Alaska this weekend. During its southeastward
travel through the Gulf, increasing winds through Shelikof
Strait, Kodiak Island and the Kenai Peninsula can be expected.
Confidence in its exact placement is moderate with its
strengthening and eastward progression toward Southeastern
Alaska. As the low strengthens and progresses eastward, the
possibility of increased gap winds return for Price William Sound
for the end of this weekend into early next week. Elsewhere, as
the high in the North Pacific moves to the southeast, signals
point toward a weak low forming and moving northeastward along
the Aleutians toward the Northern Gulf of Alaska.

-JOHNSTON

&&

.AVIATION...

PANC...VFR conditions persist. Gusty southerly winds will
gradually diminish this evening. There is uncertainty in wind
direction overnight, though winds will drop below 10 kts and
remain there.

&&