291
FXAK68 PAFC 200043
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
443 PM AKDT Thu Sep 19 2024

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

An upper-level shortwave pivots east across Southcentral tonight,
promoting showers from the Chugach Range eastward. Showers should
stay mostly confined to the mountain tops. Across the Gulf of
Alaska, a different upper shortwave and attendant surface low
track northeast across the Gulf tonight into tomorrow and then
reach Southeast Alaska later on Friday. With this system, most of
the precipitation and elevated winds will occur across the Gulf
and Southeast, however this system will help enhance precipitation
across the Prince William Sound area briefly Friday morning.
Precipitation tapers off gradually Friday evening into Saturday as
both aforementioned shortwaves exit to the east and upper-level
high pressure builds across the western and southern Mainland.
Expect mostly clear skies across much of Southern Alaska heading
into the weekend. Overnight and early morning temperatures may
approach or dip below freezing.

The front of the next system enters the western Gulf on Sunday,
lifting across the entire Gulf and reaching Southeast Alaska by
Sunday evening. Steady precipitation and sustained southeasterly
gale-force winds are expected to accompany the system.

&&


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

High pressure sits over the Bering currently and will persist
through the start of the weekend. This is good news for Southwest
Alaska as it will keep any storm systems west and south of
mainland Alaska through Saturday. Instead, weak northerly flow
across Southwest Alaska is forecast to promote dry yet cool
conditions, with overnight low temperatures dipping into the low
to mid 30s the next few nights.

Meanwhile, another round of unsettled conditions is forecast for
the Aleutians as a pair of lows dig across the island chain
tonight and again tomorrow night through Sunday morning. The first
low will be accompanied by small craft to gale force winds across
the western Bering. Adak and Atka will likely experience showery
conditions with gusts to gale force during the morning hours on
Friday. The presence of high pressure over the eastern Bering will
confine the strongest winds west of the Pribilof Islands.

Immediately following Friday`s Western Aleutian system the next
upper low is forecast to swing into the Aleutians on Saturday,
helping to establish an even broader area of elevated winds.
Widespread small craft winds across the Bering can be expected
late Saturday into early Sunday. The consolidation of the two
systems into a surface low somewhere over the AKPEN will support a
belt of easterly gales beginning from Bristol Bay and bending
southward through the Eastern Aleutians. Which should equate to
gusty conditions from Cold Bay to Unalaska. Gusts to storm force
will also be possible within the belt of higher winds, primarily
north of the Alaska Peninsula.


BL

&&


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

Long wave low pressure system will dominate the early extended
outlook over most of the state and Gulf of Alaska. Models are in
good agreement with the upper level low remaining over the
northern part of the State with with associated surface features
impacting much of the Alaskan Peninsula and Gulf region. The GFS
and Canadian models move the axis of the upper level long wave
and most of its energy farther south and east than the European,
favoring the GFS/Canadian solutions. Conversely, the GFS and
Canadian models better handle the shortwave features, south of the
Aleutians and Alaskan Peninsula with the Canadian being more
aggressive with eastward speed and intensity.

Locally heavy precipitation will spread from the Central
Aleutians, over the Alaskan Peninsula and Kodiak Island and across
the Gulf through Tuesday. Moderate rain will occur over the
Southcentral coast, with lesser amounts moving inland. The
associated surface features also bring near gale force winds with
gale force gusts over the Southern Bering, diminishing on
Wednesday. Widespread gale force winds extend along the Pacific
side of the Aleutians and AKPEN through the end of the outlook
period. Ridging high pressure over the Bearing, coupled with the
fast moving shortwaves could bring marginal gale force winds and
to the central islands and Alaska Peninsula Wednesday and
Thursday.

-DD


&&

.AVIATION...

PANC...VFR conditions and light winds will persist through Friday
with increasing clouds and a chance of an isolated rain shower by
late tonight into early Friday morning. There is high confidence
that the upper level shortwave moving through Southcentral will
bring showers over the mountains Friday afternoon, but should stay
contained to the mountains. VFR conditions should prevail at
PANC.

-TK

&&


$$