578
FXAK68 PAFC 010208
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
608 PM AKDT Mon Aug 31 2026

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

Key Messages:

- Frost Advisory is in effect overnight tonight from 2 AM to 9 AM
  AKDT for the Anchorage and Lower Matanuska Valley. Coldest prone
  locations (Butte, Muldoon, Campbell Tract, and the Eagle River
  Valley) could see temperatures near or below freezing. Main
  concern is for frost sensitive outdoor plants and vegetation.

- Marine thunderstorms along the northern Gulf Coast and east of
  Middleton Island will taper off this evening.

- Gusty offshore winds continue over the next few days with the
  strongest winds along the coast and through gaps and passes this
  afternoon and evening.

Discussion:

Today started out with snow in the higher elevations of the
Anchorage and Eagle River Hillsides as a potent and cold upper-
level low dug south from central Alaska, across Southcentral, and
now into the Gulf of Alaska this afternoon. There were reports of
around 3 inches of snow along the Eagle River Hillside this
morning. The upper-level low, as mentioned, is currently over the
northern Gulf. Coupled with ample amounts of instability, due to
the warmer water temperatures, relatively, and the cold air
associated with the system, copious amounts of lightning have
developed across the northern Gulf this morning and afternoon.
Most of the marine thunderstorm activity is east of Middleton
Island and on both side of Kayak Island. Overall, this activity is
moving southeast and will taper off through this evening as
instability lessens and it moves over the open waters of the
central Gulf. As precipitation moves from along the Northern Gulf
Coast to fully over the Gulf by tonight, showers will persist
across northeastern portions of the Copper River Basin through
Tuesday morning.

Aside from termination dust this morning and marine thunderstorms
this morning and afternoon, temperatures are expected to drop
tonight as dry air from the northwest works in across
Southcentral. A Frost Advisory remains in effect from 2 AM to 9 AM
AKDT for the Anchorage Bowl and the Lower Matanuska Valley.
Temperatures could fall as low as the upper 20s in typically
colder locations, with frost capable of occurring. Other portions
of Southcentral, including the lower Susitna Valley and western
Kenai Peninsula, will also have the potential for near-freezing
temperatures and patchy frost Tuesday morning. Wednesday morning
will remain chilly as well. However, frost potential will depend
on cloud cover. If conditions stay more on the clear side, the
airmass looks to be very similar to tonight/early Tuesday morning
with more frost potential. If there are more clouds present, this
will prevent radiational cooling from fully taking effect and thus
lower frost potential.

Gap winds through Whittier and Seward will remain elevated
through the next few days as flow will remain out of the
northwest. Gusts may relent somewhat Tuesday afternoon near Seward
as ridging builds across the area. The sea breeze from the south
may also come in briefly Tuesday afternoon before the northerly
offshore winds re-ensue Tuesday evening.

For Wednesday, a shortwave digs south from Central Alaska to over
northeastern portions of the Copper River Basin. This feature
will be pretty moisture starved, but a few showers are not out of
the question for Wednesday afternoon. A strong upper-level ridge
builds in for Thursday as all of Southcentral remains dry. The
next weather system to watch will come from the Bering on Friday
and for the weekend as the pattern will switch from dry to wet by
then.

&&


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

A vertically stacked ridge remains in place over the North
Pacific, Aleutian Chain and southern Bering. A shield of clouds
can been seen streaming across the Western Aleutians and Bering as
a series of low pressure systems ride around the ridge and move
along a front situated from the Pribilof Islands to Shemya.
Rainfall associated with the current Bering system is on track to
move east of the Pribilof Islands tonight, with the edge of its
precipitation shield clipping the southern most Southwest Alaska
coast and Alaska Peninsula through Tuesday morning. Weak impulses
of energy aloft will also be riding atop the upper ridge through
the short term period, keeping the Bering and Aleutians unsettled.
Conditions will remain relatively steady state until mid Tuesday
morning where an incoming area of low pressure to the Western
Aleutians amplifies the upper level flow and tightens the pressure
gradient at the surface between the surface low and ridging
anchored to the east. With this, high end gales and blips of
storms are showing up in the boundary layer of both the GFS and
the NAM, which suggest surface winds will most likely reach at
least low end gale force with higher gusts with the front Tuesday
morning for the Central Aleutians. At the surface, the incoming
front also puts a dent in the ridge and nudges it farther south
through Tuesday afternoon. While the parent area of low pressure
does not move much past the Western Aleutians, its front, with
help from the ridge, will funnel tropical moisture along the
boundary and will create an axis of moderate rainfall that will
traverse the Aleutian Chain. Looking at 500 mb heights and
vorticity, the models depict a "kicker" shortwave rotating around
the main closed low Thursday, which will essentially force it to
gain momentum and move farther eastward over the Bering through
Thursday morning (and increase winds underneath the forcing).
Rainfall then approaches Southwest Alaska by Thursday afternoon.


-AM

&&


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

The long-term period looks to remain active, especially across
Southwest Alaska, the Bering Sea, and the Aleutian Chain. With a
ridge axis anchored over Southcentral and the Gulf of Alaska, and
a complex low pressure system spinning about in the central Bering
Sea, Southwest Alaska appears to be the more active of the areas.

Across Southcentral Alaska, the ridge will be overhead for much
of Friday with relatively quiet weather anticipated. The ridge
moves east to the eastern Gulf of Alaska and into Yukon, Canada
Friday evening which will open the door to southwest flow aloft.
Steady rain from Southwest will move into Southcentral through
late Friday as a plethora of shortwaves lift up and over the area
from North Pacific and Gulf. Showers continue over Southwest, the
Aleutian Chain, and Southcentral for Saturday as a broad upper-
level trough remains in the Bering and southwest flow aloft
remains across Southcentral.

A series of several shortwaves spinning around the complex low in
the Bering will move from the Bering into Southwest Alaska Friday
and Saturday. By late Saturday, a compact low entering from the
northern Gulf will enter the southeastern Bering Sea with the
chance to swing into Southwest Alaska. Model agreement is poor
regarding the progression of this feature, however it may bring a
more condensed push of rainfall into the area. Also, depending on
the orientation of the southwest winds into Southwest Alaska,
coastal concerns in the Kuskokwim Delta remain present as a
possibility, but we will continue to monitor it`s progress.

-CL

&&


.AVIATION...

PANC...Generally expect a drying trend with clearing skies
throughout the remainder of the afternoon and evening. However,
there remains a small chance (30 percent) that a brief shower may
occur over the terminal through early evening. Any lingering
shower activity should be out of the area by late this evening.
Northerly winds will continue through tonight with gusts up to 25
kt likely through late this evening. MVFR ceilings this afternoon
will improve to VFR as the shower activity winds down this
evening.

&&


$$