369
FXAK68 PAFC 160051
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 PM AKDT Wed May 15 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Friday night)...

A sharp upper level ridge axis now extends from the Gulf into
Southcentral, allowing for quite the pleasant and sunny afternoon
for much of the region. Clear skies are in place under the ridge,
with the exception of a few cumulus popping up over the Mat-Su and
Copper Basin as the boundary layer deepens with daytime heating.
However, little if any shower activity is expected today due to
warmer temperatures aloft that will prevent convective cloud cover
from becoming more vertically developed.

Meanwhile, a weakening front associated with a system out in the
Bering Sea is beginning to cross over the Alaska Range into
Southcentral. Clouds and very light rain will increase first over
Kodiak Island tonight, then into the Kenai Peninsula on Thursday.
Even though the ridge axis will shift closer to the ALCan border,
it still looks like it`s influence will prevent rain from getting
all the way up into the Mat-Su and Anchorage areas, with the main
front and upper trough shunting south into the Gulf by Thursday
evening. Cloud cover will still be much higher on Thursday for all
but the Copper Basin, resulting in slightly cooler temperatures
for the western half of Southcentral for Thursday.

By Thursday night, the upper trough moving into the Gulf will
begin to close off into a low, while an attendant surface low also
moves east from Kodiak Island into open Gulf. Areas of light rain
and high elevation snow will shut off as it does so during the day
on Friday and as a weak shortwave ridge attempts to build back
into the western parts of Southcentral behind the low. This should
allow for clouds to break up somewhat, with slightly warmer
temperatures also returning to start off the weekend. On Saturday,
a more potent upper level low will slide from the Bering Sea into
the western Gulf, sending another wave of steady rain back into
Kodiak Island. Aside from Kodiak, all but perhaps the southern
coast of the Kenai Peninsula should still stay dry through
Saturday afternoon, but cloud cover will again increase throughout
the day. Southerly gap winds through the typical spots will also
pick up again as a coastal ridge develops ahead of the low
entering the far western Gulf.

-AS

&&


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

Winds are expected to gradually die off tomorrow morning with
most areas along Southwest getting calm south or southwest winds.
Rain and snow will gradually diminish through Thursday morning as
the front pushes east.

A weak shortwave will bring a quick burst of precipitation along
the Aleutians tonight and reaching the central Aleutians by
tomorrow morning before weakening south of the Aleutians. A
Kamchatka low will follow into the Bering Sea Thursday and the
next front is expected to reach the eastern Aleutians and
Pribilofs for Friday morning. Precipitation chances increase for
Friday night through Saturday as the front reaches the Southwest
Alaska. The position, speed, elongation, and tilt will be a factor
with the extent of the precipitation. The direction of the wind
field will also be affected. Therefore, confidence is still
somewhat lower though as models keep shifting agreement, run to
run.

rux

&&

.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. Winds
this afternoon are driven largely by up inlet flow resulting in a
seabreeze into PANC. Sustained winds of 10 to 12 knots appears
likely with winds eventually decreasing closer to midnight. Chance
for winds out of Turnagain Arm to increase and move over the
terminal by early Thursday afternoon.

&&


$$