377
FXAK68 PAFC 171250
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 AM AKDT Sat May 17 2025

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

Southcentral remains under a rather moist airmass with the morning
sounding out of Anchorage showing fairly saturated air up past 20K
feet. Early morning water vapor satellite imagery shows a sharp
edge to this moist air with a boundary to much drier air in the
far north Susitna Valley along the Alaska Range. Satellite shows
a very weak wave moving through Southcentral which is providing
just enough lift for some areas of rain showers from the central
Susitna Valley to northern Kenai Peninsula. This pattern is not
changing much the next few days with this moist airmass remaining
and the occasional short wave aloft producing lift for some shower
activity. By Sunday some models are increasing the instability in
the northern Copper River Basin. At this time, it looks like the
persistent cloud cover will likely be enough to suppress
convection. However, if sufficient clearing does occur, it could
open the door to some thunderstorms in the northern Copper Basin
Sunday afternoon and evening. This does not look likely at this
time but is an uncertainty that we will be watching.

&&


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

A broad, weakening surface trough still remains situated just
offshore of the Kuskokwim coastline, which is allowing for
scattered rain showers to continue for Kipnuk, Toksook Bay, and
Bethel. The trough extends farther south and west into the Bering
Sea, which has yielded a low stratus deck out ahead of a ridge
with clearing skies moving across the Pribilofs. Model guidance
shows that the trough dissipates and rain showers come to an end
by this afternoon and evening as the ridge tries to anchor itself
across the Bering Sea.

This afternoon, a fast-moving, decaying front with a quick round
of rainfall and gusty winds moves across the Western Aleutians.
This feature continues to fall apart as it treks farther south and
east into the North Pacific through midday Sunday, possibly
clipping Amchitka and Adak with light precipitation and elevated
winds before it does so. By late Sunday, a 500 mb shortwave begins
to descend from northeastern Russia. It makes its way southward
to the Kuskokwim Delta and Bristol Bay on Monday, which likely
will have enough forcing to develop showers and enhance offshore
winds for these areas.

A much more impactful system likely moves into the Western and
Central Aleutians late Monday into early Tuesday, although some of
the models slightly differ on timing of the onset of heaviest
precipitation and strongest winds. However, most of the guidance
agrees that winds could gust to gale force with the system`s
arrival.

-AM


&&



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

The broad upper level trough stretches from Siberia across the
Bering Sea and Mainland Alaska. It will be undergoing significant
changes to line up over Western Alaska through the forecast
period. In the West, a ridge builds over the Aleutians from the
North Pacific, changing the tracks of shortwaves slipping through
the pattern. A weaker ridge builds into the Eastern Interior
through the week. Model guidance with mostly ECMWF and GFS remains
in decent agreement during the changes, with a bit less
uncertainty aligned with the smaller details through Friday.

Scattered showers continue over most of the Southern Interior. A
slight chance of more convective activity is possible in the
warmest zones in Eastern Alaska. The main weather producers will
be marching over the Southern and Western portions of the state
through Friday. A well developed Central Kamchatka surface low and
front pushes across the Western Aleutians and Bering. Moderate
rain and some locally gusty offshore winds ride with the frontal
passage before diminishing across the Eastern Aleutians late
Wednesday. A second developed North Pacific low and front
approaches the Western Aleutians for Wednesday. Widespread rain
with the front sweeps across the Aleutians and Bering before the
system recurves towards the Alaska Peninsula and North Pacific for
friday. A strong third low and front awaits in the wings for the
Western parts of the state for the following weekend.

- Kutz


&&

.AVIATION...

PANC...MVFR ceilings are expected this morning with chances for
light rain. Ceilings will lift to VFR but will stay at or below
5000 ft by the early afternoon and persist through the remainder
of TAF period. There will be a bend in the Turnagain Arm wind over
the Terminal this afternoon, with southerly wind gusts to 20kt.
Winds diminish to less than 10 kts tonight but will remain
southerly.

&&


$$