High Wind Watch 12, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
503 AM AKDT Tue Oct 1 2024

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

Discussion:

The low pressure system that deepened quite rapidly yesterday over
the Gulf continues to move eastwards this morning. Satellite imagery
shows it to be tightly wound occluded system this morning as it
moves into the far western Gulf with quite a bit of dry air
entraining into it. Winds have steadily been decreasing this morning
from west to east as the system exits the central Gulf. Cloud cover
associated with this system is also steadily eroding but will likely
see some mid and upper level cloud cover linger into the afternoon
for areas along the Gulf coast. As the system moves east, the steep
pressure gradient over the coastal mountains (that resulted in gusty
winds developing through the north/south gaps and inlets yesterday
afternoon and evening) has greatly relaxed and most winds have
slackened significantly. The offshore flow and a push of dry air
from the north has allowed for dewpoints in the teens and 20s to
push into the Copper River Basin and down into the Mat-Su Valley,
though not as far south at the Anchorage Bowl. For areas in the
Copper Basin where skies have remained clear and winds have calmed,
temperatures will fall to near freezing or colder this morning.
Elsewhere, winds and/or more cloud cover will help to prevent
temperatures from falling to low. However, with clearer skies and
light winds anticipated overnight tonight, we should see more areas
reaching those colder temperatures tomorrow morning.

We will see a brief lull today before the next system moves into the
Gulf by midweek. The low will lift into the northern Gulf as it
weakens, bringing showery conditions to the coastal zones through
Thursday.

- PP

&&

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

Current satellite, surface observations and radar show widespread
clouds and showers over the Central Aleutians. These showers are
associated with a weak low that will move southeastward this
evening through the AK Pen. A second low will move through the
Bering Sea bringing continued rain to the Central Aleutians
tomorrow. The rain will stretch into the AK Pen tomorrow evening.
Overall amounts remain light with two-day totals ranging from
0.20 to 0.02 inches. In addition to this rainfall, wind gusts
ranging from 20 to 30 mph are likely through tomorrow. Weak
ridging builds into Southwest Alaska today.

Confidence continues to increase to moderate that a fall
Kamchatka Low will move into the Bering Sea later this week.
A low pressure system from the remnants of Typhoon Jebi will move
into the Bering Sea. Current tracks and guidance indicate this
low would deepen in the Bering Sea Thu/Fri and move east-
southeastward toward the Pribilof Islands and AK Pen. West-
northwest hurricane force winds on the backside of this low as
early as Thursday afternoon in Shemya and Thu evening/Fri morning
in Central Aleutians are probable. Sea heights are expected to
increase in conjunction with these winds as well.

-DJ

&&

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

The focus in the long-term continues to be a strong storm system
moving from the southeastern Bering late Friday across the AKPen
and into the western Gulf by Sunday morning.

There is high confidence that sustained winds will reach storm
force (55-73 mph), with embedded hurricane force (> 73 mph)
gusts across the central and eastern Aleutians Friday as the
storm system reaches its maximum intensity. As the low moves south
of Kodiak Island Saturday, gusty northwesterly winds will continue
across the eastern Aleutians and AKPen, albeit slowly trending
downward, with widespread gale-force winds and storm-force gusts,
through the weekend.

Farther east, the occluded front associated with the low will
parallel the Southwest Alaska coast Friday morning, bringing rain
and southeasterly winds up to 50 mph for coastal communities. The
storm track has shifted a bit farther south and west in recent
runs, and, as such, the predominant east-southeasterly winds along
this front should keep any coastal flooding concerns at bay.
Interior Southwest will also see an increase in gap winds on
Friday, with these winds becoming more easterly through the day
before shifting to the northeast and diminishing on Saturday.

The aforementioned occluded front enters the western Gulf late
Friday with rain and strong easterly gales across Kodiak Island.
The front then lifts to the north Gulf coast Saturday morning as
the parent low moves south of Kodiak Island. Discrepancies in the
track and timing of northward progression of the front grow by
Saturday; however, expect a strong easterly barrier jet to develop
along the coast at some point on Saturday. The east-southeasterly
flow aloft out ahead of the front will also drive copious amounts
of moisture into the coast and over the coastal mountains.
Precipitation will continue into Sunday; however, the position of
the front will dictate where the heaviest precipitation falls.
Currently, the EC and GEM drive the front inland with the waves of
more showery precipitation moving south to north, potentially
bringing heavier rain to places like Seward and Valdez. The GFS
keeps the front offshore, with a persistent easterly flow favoring
heavier precipitation from Cordova through Prince William Sound
into Whittier.

Whatever the solution, expect unsettled conditions along southern
coast, AKPen, and eastern half of the Aleutian Chain through the
weekend with gusty winds and rounds of moderate to heavy rain.

-TM

&&

.AVIATION...

PANC...VFR conditions and light southerly winds are expected
through the forecast period.

&&