Gale Warning 412, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
433 PM AKDT Fri Jun 9 2023

.ANALYSIS AND UPPER LEVELS...

The broad upper level low in place over the Aleutians continues to
slowly drift southward. Satellite imagery confirms widespread low
level stratus over the southern half of the state. As several
weak upper level waves continue to rotate around the low,
scattered showers persist across the northern Gulf coast, Cook
Inlet region, and inland locations of Bristol Bay and the Alaska
Peninsula.

&&

.MODEL DISCUSSION...

Model solutions are in good agreement through the next 24 hours
and seem to be better aligned with the position of the next North
Pacific low arriving over the Alaska Peninsula/Kodiak Island on
Saturday night. While models suggest varying strengths of this
low, there is high confidence that widespread gale force winds
will impact the marine areas from the southern Alaska Peninsula
to the northern Gulf coast.

&&

.AVIATION...

PANC...Gusty south to southeast winds will continue. Rain may
develop early Saturday morning which could lower ceilings under
5000 ft, though generally VFR conditions are expected.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This
afternoon through Monday afternoon)...

Southeasterly gap winds have ensued this afternoon with day-time
heating through Turnagain Arm, Knik Arm, and the Copper River
Valley. However, mostly dry and sunny conditions have prevailed;
particularly for Anchorage, the Mat-Su Valleys, and the Copper
River Basin. Although, there are a few showers around the western
facing slopes of the Talkeetna Mountains as well as the Wrangell
Mountains this afternoon.

An upper-level low centered around the Aleutians pushes a
shortwave trough northward through the southern Gulf of Alaska
this afternoon. Kodiak Island will continue to see scattered
showers into the evening hours before tapering off overnight.
Rain will also continue to pick up for the eastern Kenai Peninsula
as the trough continues to lift northward. This trough, and the
accompanying rain, eventually makes it to the north Gulf coast
overnight tonight into Saturday. There could be a passing shower
or two for Anchorage and the Matanuska Valley Saturday as the
trough passes over and continues inland. Meanwhile, the Susitna
Valley and Copper River Basin will see also see a few showers.
However, the lack of day-time heating and cloud cover should
mitigate thunderstorm development. Expect another round of
southeasterly gap winds with the trough passage Saturday
afternoon.

The bigger weather story will be an anomalously strong low
pressure system forecast to move northward from the North Pacific
to the southern Alaska Peninsula Saturday night. This low will
send a gale-force front northward through the Gulf of Alaska to
the north Gulf coast late Saturday afternoon through Sunday
afternoon. There could be a pocket of storm-force winds near the
Barren Islands early Sunday morning as the pressure gradient
tightens further. Of note, gap winds will also be stronger as the
front moves inland Sunday. Small craft winds are likely through
Prince William Sound and Passage Canal Sunday morning into the
afternoon.

Precipitation-wise, Kodiak Island will be the first to encounter
moderate to, at times, heavy rain Saturday evening. The heavy rain
threat then moves to moves to the eastern Kenai Peninsula Sunday
morning and to the rest of the Gulf coast through the day on
Sunday. Anchorage, most of the western Kenai Peninsula, and
the Matanuska Valley should remain mostly dry Sunday due to
downsloping southeasterly flow. Parts of the western Susitna
Valley could see a few showers with upslope flow against the
Alaska Range. Flow looks to become more southwesterly in the
middle to upper level into Monday. Thus, usual downsloped areas
have a chance to get in on some rain showers as the upper-low
responsible for the gale-force front lingers in the eastern
Bering Sea.

&&

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

The pattern remains relatively the same, with broad low pressure
stretching across the Bering Sea and Southwest Alaska. Light,
showery conditions will continue across Southwest through the
weekend. There may be intermittent breaks in the clouds between
rain showers which could allow some brief periods of sunlight at
times, though anticipate it being short-lived. An unseasonably
strong area of low pressure moves out of the North Pacific towards
the Alaska Peninsula Saturday afternoon. Winds across Southwest,
primarily out of Kamishak Gap across portions Bristol Bay, and
heavy rain are expected, with the heaviest precipitation expected
to fall along the Alaska Range. Excessive rainfall over low lying
areas may produce localized flooding and an Special Weather
Statement has been issued to address this concern. Additionally,
gusty winds will be prevalent along the eastern Bering Sea, with
some gale force gusts spreading across Bristol Bay. The low will
then move northwestward, scooting along the Southwest Coast
through late Sunday. There is still some model disagreement from
Sunday and beyond, particularly regarding winds, with the GFS
showing much stronger onshore winds compared to the NAM.

&&

.LONG TERM FORECAST (Days 4 through 7/Tuesday through Friday)...

A broad upper level trough remains anchored over the Bering. This
will generate widespread showers across the Aleutians, Alaska
Peninsula, and southwest Alaska through Wednesday. Farther north
over the Arctic Ocean, a strong upper level low extends southward
through Thursday and effectively re-energizes this trough. Would
expect to see continued unsettled conditions for the Bering,
Aleutians and Southwest coast through Friday. Meanwhile for
Southcentral, a weak ridge tries to build over the Gulf on
Wednesday, however is quickly pushed eastward as the upper level
Bering trough advances from the west. An unsettled pattern will
remain as multiple upper level waves traverse Southcentral
through the end of the workweek, keeping showers in the forecast.

&&

SYNOPSIS AND MODEL DISCUSSION...KO
SOUTHCENTRAL ALASKA...DAN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KM
LONG TERM...KO