159
FXAK68 PAFC 201341
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
541 AM AKDT Sat Jul 20 2024

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

The warmer and drier weather is expected to persist through the
weekend. Embedded easterly waves will move across Southcentral
this weekend. While most areas will stay dry, there is a chance of
isolated showers over the Copper River Basin and Mat-Su Valleys
today with increasing chances for isolated thunderstorms Sunday as
warmer temperatures and more instability are expected. Depending
exactly where exactly the mesoscale waves track, the Chugach and
Kenai Mountains, including potentially the Anchorage Hillside, and
along the lee side of the Kenai Mountains, have a chance to see
an isolated storm for Sunday afternoon and into the evening.
However, confidence is low for where exactly these thunderstorms
will develop due to subtle differences in the tracks of the
mesoscale waves. The warmest locations this weekend will continue
to be the Copper River Basin and Susitna Valley where temperatures
could touch 80 degrees. The warmer and drier weather comes to an
end on Monday as a more energetic easterly wave from moves
westward starting in the Copper River Basin by Monday morning and
then the rest of mainland Southcentral Monday afternoon.
Precipitation weakens by Tuesday morning as upper level support
degrades significantly and phases with a weakening front over
Southwest Alaska Tuesday night.

&&


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

Current satellite and observations show an occluded low near the
Western Aleutians and a ridge over Southwest Alaska and areas of
patchy fog on the Southwest and Aleutian coastlines. The low`s
occluded front is bringing cloudy conditions and rain showers to
the Central and Eastern Aleutians as Pacific Ocean moisture moves
northward. The front will dissipate Sunday as it moves eastward
with the building of a ridge over Southwest Alaska.

Observed rainfall totals over the past six hours vary from 0.1"
to 0.14" in the Central Aleutians. The greatest amounts are in St`
Paul Island and Unalaska with the least towards Port Heiden.
Periods of rain are expected into tomorrow afternoon in the
Central Aleutians as the aforementioned front slowly moves
eastward resulting in 0.50" to 1.00" of total rain this weekend.
Wind gusts through the gaps will range from 30 to 40 mph with
gusts elsewhere ranging from 20 to 30mph today. These gusts will
diminish overnight into tomorrow morning. Isolated thunderstorms
are possible in the Bristol Bay and Western Alaska Range areas
tomorrow.


-DJ

&&

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

With some small adjustments with the position and strength of the
omega block over Mainland Alaska will come from the West through
the forecast period. One upper level low center exits the Gulf of
Alaska Wednesday with little effect to the high, moving onshore
into Canada by midweek. The other low in the Bering gathers
support from the Arctic and begins its move over the West Coast.
Shortwaves around the Bering low add increased instability for the
Western half of the state. Longer term rainfall continues across
the Aleutians and Bering through the end of the workweek. Forecast
model confidence remains higher for the Interior features, and
slightly less elsewhere. Periods of locally heavy rain spreads
over Southwest Alaska and the Alaska Peninsula for late Tuesday
and is sustained more over the West as the areal coverages expands
across Kodiak Island and Southcentral Alaska through Prince
William Sound by Friday. Locally heavier rains will also extend
inland to the Alaska Range during the forecast.

The Eastern Interior and along the Alaska Range will see warmer
temperatures as the bulk of the surface high holds in place
through the Yukon Valley. A higher risk of occasionally heavier
showers and thunderstorms through the Copper River Valley are
possible through the forecast period.


- Kutz

&&

.AVIATION...

PANC...VFR conditions will prevail. Turnagain Arm winds will be
possible this afternoon with gusts of 15 to 20 kts. Winds will
shift to the west tonight and gradually weaken tonight into Sunday
morning. Then, light winds will prevail. Vicinity showers and
isolated, vicinity thunderstorms could develop near the foothills
of the Chugach mountains Sunday afternoon.

&&


$$