853
FXAK68 PAFC 071330
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
530 AM AKDT Tue May 7 2024

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

A few showers remain this morning across far western Cook Inlet and
nearby Alaska Range. Ongoing showers also noted across the northern
Gulf and Prince William Sound in the vicinity of a weakening low
pressure system. Showers have also begun again for Kodiak Island as
the next system lifts up into the Gulf. Elsewhere across
Southcentral, much of the cloud cover has moved out resulting in
clearing skies for the western Kenai north into the Mat-Su Valley,
and the Copper River Basin. With the recent rainfall across much
of this area, and generally light winds...some areas may see some
patchy fog develop this morning.

The weather should remain fairly quiet today with just some
diurnally driven showers developing along the higher terrain and
increasing precipitation chances for the Gulf Coastal zones as the
next system advances.

The low moving up out of the north Pacific will trek towards the
north-central Gulf by Wednesday morning and cold air working in
behind the system. The bulk of the precipitation still looks to
push towards Southeast Alaska at the start, but the low looks to
retrograde back to the west before moving inland near Prince
William Sound. As such, coastal areas should see precipitation
increase Wednesday as the low moves back west. There are some
model discrepancies as to how far west the surface low moves,
which will impact rainfall amounts for the western Prince William
Sound and eastern Kenai. Strong winds will also accompany the low
with gales likely to the north of the the surface low in the
northern Gulf coastal waters.

Beyond Wednesday remains a bit nebulous, as the bulk of the med and
long-range model guidance has picked up on a polar low developing
near the Bering Strait then rapidly translating across the Bering
before curving slightly north towards the AKPen. If this polar low
materializes, we would see the mid to late week system moving up out
of the northern Pacific shunted eastwards into the eastern Gulf
taking the much of the precipitation with it...keeping Southcentral
on the cooler and somewhat drier side.

- PP

&&


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

Unsettled conditions with areas of mixed rain/snow will continue
across much of interior Southwest Alaska through midweek as a
stalled surface boundary remains draped from near King Salmon to
north of Aniak. These areas of showers will be enhanced both
Tuesday morning and again Wednesday as a series of weak upper-
level waves moves across the region from the west. These waves
are moving out ahead of the main upper-level, longwave trough
situated over the eastern half of the Bering.

A potent shortwave trough will move south from the Bering Strait
Tuesday morning to the Pribilof Islands by Wednesday morning. This
feature will deepen into an upper-level low. This, combined with
cold, dense air near the surface advecting from the Gulf of Anadyr
over the northern Bering, will result in the development of
compact polar low. While guidance continues to struggle with the
exact timing and track of this feature, it will most likely deepen
rapidly as it moves from west of Saint Matthew Island south
toward the Saint Paul Island.

A core of gale-force winds and storm-force gusts are likely along
the western flank of the low, with gales persisting along the way
to the eastern Aleutians and Alaska Peninsula as late as Thursday
morning. A core of snow will also accompany this system. Again,
the exact setup remains uncertain, but a track over or very near
the Pribilofs could bring at least some measurable snow along with
gusty winds.

This low reaches Bristol Bay for Thursday with showers for the
AKPen and Bristol Bay coast. Another deep low moving east from the
Kamchatka Peninsula will push a gale-force front across the
western Aleutians for Wednesday and the central Aleutians for
Thursday.


&&

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

The longterm forecast begins on Friday with broad troughing
continuing to stretch from the western Aleutians into the Gulf of
Alaska, with multiple upper-level shortwaves embedded within the
flow. At the surface, a system weakens over Southcentral on Friday
while an expansive low encompasses much of the Bering and the
Aleutians. This low is associated with a potent upper shortwave
that forms into a closed upper low and lingers near the Alaska
Peninsula through at least the weekend. Multiple shortwaves rotate
around the low as the attendant surface low gradually drifts
closer to the Gulf of Alaska. As a result, precipitation is
expected for Southwest Alaska, the Gulf, and the northwest Gulf
coast for Friday and Saturday. Precipitation will especially be
focused on the upslope sides of the mountain ranges while lower
lying valley areas should stay on the drier side of things. By
Sunday, the low`s front spreads across the entire Gulf coast and
still portions of Southwest Alaska, however models struggle with
regards to the placement of the low center. The GFS keeps the low
further west near the eastern Bering/Alaska Peninsula, while the
CanNH and EC bring the low east into the Gulf. The GFS solution
keeps the precipitation a bit steadier along the Gulf coast while
the others break the system up over land, lessening the chances of
precipitation.

&&

.AVIATION...

PANC... Light and variable winds this morning to persist into the
early afternoon with a return of the Turnagain Arm wind expected
after 21Z today. Rain should be over until Wednesday evening and
VFR conditions are expected into Wednesday; however, some
diurnally driven showers are possible. Return to lower ceilings
and rainy conditions possible by Wednesday afternoon.

&&


$$