618
FXAK68 PAFC 182348
AFDAFC

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

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

Southeasterly gap winds of 20 to 35 mph through Turnagain and
Knik Arms and in the Copper River Basin this afternoon will
slowly diminish tonight as a front over the Gulf lifts northward.
Cloud cover and upslope showers along the coast will increase in
coverage through early tonight as the pattern turns wetter and
relatively cooler for Sunday and Monday.

A surface low currently located over the Alaska Peninsula with
strong upper level support and an unseasonably cold upper level
low continues to push eastward and will be over Kodiak Island by
Sunday morning. This is currently sending 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, while not as strong as Saturday,
gusty southeasterly gap winds returning during the afternoon
Sunday. With unseasonably cold temperatures aloft, any heavier
precipitation rates may allow some snow to mix in with the rain in
the Copper River Basin Sunday night. The low continues to weaken
on Monday as it pushes north and east into the Northeast Gulf of
Alaska, with unsettled conditions over Southcentral continuing,
especially in the Copper River Basin. Expect decreasing clouds and
precipitation on Monday night and early Tuesday as a weak ridge
builds into the northern Gulf of Alaska.

A low over the Bering pushes another front into Southcentral
Tuesday morning, with rain likely overspreading much of
Southcentral by late Tuesday afternoon. With a more
southerly/southwesterly flow aloft, the western Kenai, Anchorage
Bowl, and MatSu looks to see some rain with this system as well.

-ME

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3: This Afternoon through Tuesday
Evening)...

The forecast remains on track in the short-term. The negatively
tilted trough and upper-level low will continue to move eastward
to the Gulf of Alaska tonight and through Sunday. Shower activity
over the Southwestern mainland will begin to taper off Sunday as
the energy and low pressure shifts to the Gulf. Showers could
still persist through Sunday for interior locations of Southwest
as weak shortwaves wrap around the Gulf low.

Out west, a series of Kamchatka lows and fronts will begin to
impact the Bering Sea and Aleutian Chain. The first frontal system
is currently over the western Bering and western Aleutians
spreading rain and small craft winds as it moves to the east. This
front will begin to weaken and dissipate Sunday evening before it
reaches the Pribilof Islands and eastern Aleutians. However, the
second system, a Kamchatka low, will enter the western Bering by
then and absorb the remnants of the weakening front as it
continues to move eastward. This now energized front will make it
to the Pribilof Islands Monday morning. Light to moderate rain can
be expected to accompany this system as well as small craft
winds. The majority of precipitation will fall along the Pribilofs
with eastern Aleutians and southern Alaska Peninsula seeing
scattered showers for Monday.

The front of the now central Bering low will reach the
southwestern mainland coast by Monday afternoon. Coastal Bristol
Bay and coastal Kuskokwim Delta look to receive the most
precipitation with the heaviest falling Monday evening and through
the overnight hours. The front continues pushing eastward and
inland through Tuesday with interior Bristol Bay and the Lower
Kuskokwim Valley seeing steady rain throughout the day. As the now
occluded low continues working eastward, cold air could sneak
back in to the Kuskokwim Delta coast and especially Nunivak
Island, where there could be a period of rain/snow mix before
temperatures warm through the day. Another, potentially gale-
force, North Pacific low looks to impact the western Aleutians and
western Bering starting Tuesday evening with rain and gusty
winds.

&&

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

A persistent northwest to southeast oriented longwave trough will
remain over the Bering with a shortwave on the southern terminus bending
into the northern Gulf through Sunday. A second upper level low
will move from Kamchatka into the central Bering on Tuesday
followed by a third on Thursday. This series of low pressure
systems will bring gusty wind, coastal rain showers and interior
cloudy and isolated rain showers. Toward the end of next week, an
area of high pressure will push from the North Pacific into the
Bering Sea and nudge the longstanding trough eastward.

&&

.AVIATION...

PANC...VFR conditions will persist. Strong southeasterly winds
out of Turnagain are expected to persist past midnight tonight. It
does look like the Turnagain Arm winds will then turn down the
Inlet as a low moves along the southern Kenai Peninsula overnight
and turns the pressure gradient down-Inlet. There is the potential
for some wind shear when this happens, but it will likely be above
2000 ft.

&&


$$