882
FXAK68 PAFC 181311
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
511 AM AKDT Sat May 18 2024

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

Ridging will build north out of the Gulf into Southcentral
today, ahead of a low pressure system pushing east of of Bristol
Bay into the Western Gulf of Alaska. This will bring seasonal
temperatures and relatively dry conditions today. Southeasterly
gap winds of 20 to 30 mph are expected through Turnagain and Knik
Arms as well as along the Copper River in the Copper River Basin
this afternoon. Temperatures will reach the mid 50`s to near 60 in
the Western Kenai, the Anchorage Bowl as well as the Matanuska
and Susitna Valleys this afternoon. Temperatures will reach into
the lower to mid 60s in the Copper River Basin. Cloud cover and
upslope showers along the coast will increase in coverage Saturday
evening through early Saturday night as the pattern turns wetter
and relatively cooler for Sunday and Monday.

A strong surface low currently located just west of Bristol Bay
with strong upper level support and unseasonably cold upper level
low over the Bering Sea will strengthen as it pushes east over the
Alaska Peninsula today and over Kodiak Island by Sunday morning.
This will send another period of precipitation back into the
island. As the upper low and accompanying surface low move into
the western Gulf, precipitation will also overspread the eastern
Kenai Peninsula and into the Prince William Sound through Sunday
morning. As the upper low hugs the coast and moves inland,
shortwaves on its western periphery will allow precipitation to
fill in over the Copper River Basin late Sunday into Monday. The
Eastern Kenai and Prince William sound will see the heaviest
precipitation while the Western Kenai, the Anchorage Bowl and the
MatSu will see lesser amounts with drying downslope flow and gusty
southeasterly gap winds. The low continues to weaken on Monday as
it pushes north and east into the Northeast Gulf of Alaska. Expect
generally unsettled weather over Southcentral on Monday especially
in the Copper River Basin. Expect decreasing clouds and
precipitation on Monday night and Tuesday as a weak ridge builds
into the northern Gulf of Alaska.

-CC

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3: Today through Monday night)...

The forecast remains on track, with only minor updates to the
near-term. Forecast confidence diminishes by Sunday afternoon, so
stay tuned as we continue to update the forecast. No major hazards
are being monitored at this time.

Diving into the details... an active weather day is in store for
Southwest Alaska as two lows merge near Bristol Bay, pushing the
resulting front inland. Both the Bethel and King Salmon radars are
beginning to pick up on precipitation moving in with the front.
With temperatures hovering at or slightly above freezing, Mekoryuk
and Toksook Bay are currently reporting light snow. Otherwise,
warmer temperatures will keep precipitation all rain throughout
the remainder of the region. In addition to precipitation, expect
gusty east to southeasterly winds through Kamishak Gap and across
much of Southwest Alaska. Strong winds aloft will also help aid in
downslope drying, keeping interior communities along the western
slopes of area mountains drier than their coastal counterparts.
Conditions should improve through Sunday as the low and its front
depart into the Gulf of Alaska.

Active weather is also expected for parts of the Aleutian Islands
and Alaska Peninsula today, but to a lesser extent than what`s
forecast for Southwest Alaska. With the front having already moved
past it, the Eastern Aleutians will stay relatively dry. Expect
scattered showers but no steady precipitation. Instead, the main
focus for the Eastern Aleutians and Alaska Peninsula will be gusty
northwesterly winds, aided by an incredibly robust upper level
shortwave rotating around the low. Further west, the Western
Aleutians will see steady, light rain and winds to small craft
speeds (25 kt) as an occluded front moves through. The Central
Aleutians, situated between these two systems, should enjoy a
fairly quiet Saturday.

Another storm system is on the way for the Bering Sea and
Aleutian Islands by Sunday afternoon/evening (and reaching
Southwest Alaska by Monday afternoon), but forecast confidence is
currently low. There remains some model discrepancies as two lows
phase: one moving eastward from Kamchatka Peninsula and another
moving in from the northern Bering Sea. The strength of the
resulting low seems to be decently well-handled; there is
consensus that a broad 990-1000 mb will form, with winds to small
craft speed and a relatively weak moisture tap. However, the
timing and position of this low is still subject to uncertainty.
Stay tuned as we update the forecast.

-KC

&&


.LONG TERM FORECAST (Days 4 through 7)...

A persistent northwest to southeast oriented longwave trough will
remain over the Bering with waves of lows moving into the
northern Gulf during much of the first part of the extended
period. This series of low pressure systems that move through the
Alaska Peninsula and into Kodiak Island will bring coastal rain
showers and interior cloudy and isolated rain showers. Toward the
end of next week, a stronger low pressure system will move
through Shemya into the Bering Sea and push the longstanding
trough eastward. Indications are that the persistent trough and
strong low could move in a more northeastward direction as high
pressure progresses northward through the north Pacific.

- DJ

&&


.AVIATION...

PANC...VFR conditions and light winds will persist through
Saturday morning. Gusty southeasterly winds out of Turnagain Arm
are expected to develop Saturday afternoon and are expected to
bend over the terminal with gusts to 25kts possible late Saturday
afternoon and evening.


&&


$$