180
FXAK68 PAFC 161244
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 AM AKDT Thu May 16 2024

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

A pattern shift is ongoing over Southcentral as the high amplitude
ridge over the Copper River Basin slowly retreats to the east and
a deep longwave trough over the Eastern Bering Sea and Western
Alaska slowly pushes to the east over the next several days.
Clouds cooler temperatures and increased chances for rain will
replace the warm and drier weather of the last couple days.

A front wrapping around a weak low pressure system pushing north
and east into the western Gulf of Alaska this morning and over
Kodiak Island this evening will bring an increase in clouds,
periods of light light rain into Kodiak Island and the Kenai
Peninsula this morning. The ridge over the Copper River Basin will
continue to slowly move to the east and as the low over the Gulf
of Alaska slows and weakens over the Northern Gulf of Alaska
today with precipitation holding off until this afternoon for the
Anchorage Bowl and MatSu areas. Cloud cover over the area will
shave a few degrees off of the high temperatures that we have seen
the last couple of days with the exception of the Copper River
Basin where clouds will hold off until this evening. Winds will
generally be light except for typical southerly gap wind locations

-CC

&&


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

The front associated with the weakening Kamchatka low continues to
drift eastward, producing rain and snow for much of Southwest.
This trend will continue through Friday afternoon before the
system dissipates. Additionally, a shortwave low is quickly
passing through the western and central Aleutians this morning,
providing a quick spurt of precipitation before it exits into the
North Pacific.

The next focus of attention will be the formation of an upper
level trough in the northern Bering starting Friday morning. The
trough will begin to swing southwards towards the eastern
Aleutians and Alaska Peninsula throughout the day Friday into
Saturday morning. Most of the eastern Bering will see
precipitation Friday afternoon through at least Saturday evening.
Some locations near the coastline across Southwest could also see
precipitation as the system treks southward. Colder air from the
Arctic will also be dragged down with this system, increasing the
potential for snow to occur at least in the morning hours of
Friday and Saturday. As the trough tilts near the AKPEN on Saturday,
increased southeasterly flow aloft and a tightening pressure
gradient will support increased winds across the region, as well
as stronger gap winds in areas like Kamishak gap. Models are still
struggling with the progression of the system, especially as the
trough tilts negatively over the AKPEN sometime on Saturday. With
that said, model guidance does agree broadly on the trend of how
this system will develop through the forecast period.

Lastly, a new shortwave trough will begin to impact the western
Aleutians and Bering starting Saturday afternoon. Small craft
force winds gusts are possible, and widespread precipitation
mainly in the form of rain is currently expected as the shortwave
moves eastward.

-BS

&&

.LONG TERM FORECAST (Days 4 through 7: Saturday through
Wednesday)...

The long-term period begins with an upper-level trough situated
over the Eastern Bering Sea and weak ridging over Southcentral and
the Central/Western Aleutians. This upper-level pattern will be
represented at the surface by a surface low in the Eastern Bering pushing
a broad frontal boundary into Southwest Alaska and the Alaska
Peninsula. At this time, Southcentral will likely be under the
influence of the ridge, this may manifest as more clear skies,
however the chance for a mid-level stratus deck is possible. By
Sunday morning however, the low is expected to track across the
AKPen, entering the Western Gulf of Alaska, spreading a
potentially heavy, but relatively brief, shot of rainfall across
coastal locations of Prince William Sound as well as Kodiak
Island. Model agreement up to this point in time is fair with some
slight variations, but the overall themes and timing represented
well throughout. By Sunday afternoon however model solutions
diverge sharply, with some solutions lingering the low across the
northern Gulf, and others more transient, shifting the low off to
the eastern Gulf by late Sunday. Additionally, Sunday afternoon in
the Bering has very little agreement with regards to timing,
features, and persistence. Generally, a trough will build over the
Bering into the early portion of next week, however at this time
little more details on impacts at the surface, and overall
timing/progression of this system are discernible.

-CL

&&

.AVIATION...

PANC...VFR conditions anticipated through the TAF period.
Turnagain Arm winds increase this afternoon and are expected to
bend into the airport. Sustained southeasterly winds around 15
knots with gusts as high as 22 knots should persist into the
evening hours and possibly through the early morning hours on
Friday before the pressure gradient across the region relaxes.

&&


$$