338
FXAK68 PAFC 090044
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 PM AKDT Wed May 8 2024

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

A shortwave is lifting north through Southcentral this afternoon,
spreading precipitation across Prince William Sound and the Kenai
Peninsula. Warm temperatures and breaks in the clouds are
allowing some of the precipitation become more showery and
convective. Cooler air following this trough will bring snow
levels down and the potential for snow or a mix of rain and snow
is possible through the rest of the week.

Looking at the pattern into the remainder of the week, things
will look much more reminiscent of fall than late spring. As the
shortwave trough and low moves inland this evening, rain and
higher elevation snow will spread from the coast into interior
Southcentral. Lighter rainfall is expected to briefly lift past
lower elevations of the Copper River Basin, with amounts of
generally a tenth of an inch or less through tonight not expected
to noticeably exacerbate ongoing flooding concerns across the
Glennallen area.

Late tonight into Thursday morning, steady rain will end from
south to north as the shortwave trough exits towards the northern
Alaska Range. Rapid pressure rises at the surface behind the
trough passage will also lead to a short lived burst of stronger
gap winds late tonight into early Thursday, most notably out of
the Copper River up into Gulkana/Glennallen. Turnagain Arm winds
could bring gusty winds to Anchorage. Gap winds will also be
reinforced by a push of cold air advection from the south until
the pressure gradient weakens along the coast later on Thursday
morning. Cooler than average temperatures will prevail as cooler
air streams in from the Gulf, with widely scattered rain showers
and mountain snow showers expected to persist in general.

The main low in the Bering will swing east into Kodiak Island and
the western Gulf by Thursday afternoon, pushing another wave of
showers past Kodiak before becoming yet another open wave trough
on approach to Southcentral. There is some lingering uncertainty
regarding the exact trajectory with the main energy with this
trough, but overall expect more cold rain to spread back into the
Prince William Sound and out to the Mat-Su/Anchorage areas as the
wave lifts north late Thursday night into Friday morning. Low
level temperatures will start out noticeably cooler than what we
have for this evening`s rainfall event. While accumulating snow is
not likely down to sea level, we very well could see falling snow
reach all the way down to sea level for a short time late
Thursday night into Friday across the Mat-Su and Anchorage before
the trough axis lifts to the north on Friday. Cooler than normal
but drier conditions (except near Kodiak) will persist into
Friday.

-AS/rux

&&


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

A broad upper low resides over the central Bering Wednesday
afternoon with weak high pressure over Southwest Alaska and the
Western Aleutians. Low pressure over the Gulf of Alaska and
ridging over the Alaska mainland has aided in easterly wave
activity into interior Bristol Bay, with models suggesting
showers could continue through Thursday morning.

A polar low southeast of the Pribilof Islands moves southeast
towards the Alaska Peninsula. The low will bring below freezing
temperatures, gusty winds, and snow showers. The combination of
winds and snow could result in periods of reduced visibility at
times. Gusty conditions are expected to linger into Thursday
morning from Nikolski to Akutan. Widespread small craft winds
will occur near the polar low, with gusts upwards of 45 mph.

After the polar low departs the Aleutians and moves towards
Southwest, a Kamchatka Low is forecast to spread a broad front
into the Aleutians and Bering through Friday morning. Widespread
precipitation and gale force winds will accompany the front and
span the Aleutian Chain as it tracks from west to east, beginning
Wednesday night. Warm air along the front should lift
temperatures across the Aleutians above freezing, making most
precipitation come in the form of rain. The low will reach
Southwest by Friday morning before a new low forms southwest of
Shemya Friday afternoon.

BS

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

The Alaska weather map shows a very broad upper level trough
stretching from the Western Bering to the Canadian border. A
number of occasionally vigorous troughs work through the pattern,
picking up energy from the North Pacific and helps relax the
overall amplitude of the trough into a more or less zonal flow
through midweek. A couple of weakening low centers slip across
from Bristol Bay along the North Gulf Coast through Wednesday,
with most of the active weather production in their tracks. A
moderate ridge over the Russian Far East flattens out with help
from troughs moving out of Siberia late Monday into Tuesday.

A surface low near the Shumagin Islands with its front extending
into the Gulf of Alaska pushes most of its precipitation ahead of
the front. Locally heavy rainfall is expected from the Eastern
Kenai Peninsula, and diminishes over Prince William Sound to the
Canadian Border through Monday. Lesser amounts will occur further
inland to the Alaska Range. A well developed low near Kodiak
Island and its front spreads another period of rainfall across
Southcentral Alaska through Wednesday. A moderately strong trough
drags another area of precipitation across the Aleutians and
Alaska Peninsula Sunday and Monday. A new front out of Russia
enters the Western Aleutians and Bering Tuesday, moving across the
Central Aleutians by Wednesday. A third weather producer out of
Russia approaches the Western portions for Wednesday.


- Kutz

&&

.AVIATION...

PANC...VFR ceilings through late afternoon will likely lower to
MVFR by this evening and remain through Thursday morning. Variable
winds will become southerly by late this afternoon and will
increase tonight as an area of low pressure moves from Prince
William Sound inland over Southcentral Alaska. South to
southeasterly winds could gust as high as 35 mph tonight through
early Thursday morning before diminishing in intensity. Rain
showers are also expected to develop over the terminal this
afternoon or evening. The rain showers will become heavier tonight
with reductions in visibility to MVFR conditions possible.
Showers will become more sparse and taper off Thursday morning.


&&


$$