948
FXAK68 PAFC 090022
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
422 PM AKDT Mon Jul 8 2024

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

The main weather feature for Southcentral is a North Pacific low
which has lifted into the Western Gulf. This low will push a
front to the southern mainland tonight and bring widespread
rainfall along coastal areas into Tuesday. Rainfall is not
expected to push very far inland as the increasing pressure
gradient will produce southerly gap winds and downslope flow,
which will limit rain chances for inland areas. Elsewhere on
Tuesday, another upper level low digs southward from the Arctic
Ocean into the Bering Sea. High clouds ahead of this low may
reduce the amount of sunshine across Southcentral, with more rain
finally arriving Thursday. The amount of phasing between these two
systems is yet uncertain. To escape this late- Summer pattern,
the best chance for fewer clouds might be found in the Copper
River Basin from Tuesday night into Wednesday morning.

&&


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

A high-amplitude blocking ridge will remain over the west coast of
the U.S. and Canada through at least midweek. The result will be
the development of a deep, negatively tilted, longwave trough over
Southwest Alaska, extending into the Gulf of Alaska. Currently, a
vertically stacked low south of Kodiak Island anchors the
longwave trough with multiple shortwaves upstream of this low.

The main upstream feature is a shortwave moving across the Bering
Strait this afternoon. This feature is driving a potent surface
low east into Norton Sound along with a trailing cold front
extending into the northern Bering. Out ahead of these features
sits an elongated upper-level ridge extending from Bristol Bay
across the Alaska Range. Here, cloud cover is more scattered this
afternoon, but clouds will be on the increase starting this
evening as the surface low and front advance toward the coast.

The low and its attendant front move onshore Tuesday morning. A
deep moisture fetch, along with southerly winds, will advect ample
moisture over the Kuskokwim Delta, resulting in widespread
rainfall. The front then slows and stalls over the Kuskokwim Delta
with the parent low sliding south. The upper-level shortwave then
becomes negatively tiled across the Southwest Alaska coast for
Wednesday morning. The combination of the stalled front and
negatively-tilted shortwave will keep the axis of precipitation in
a line from Togiak to Aniak. It is in this line that the heaviest
precipitation, on the order of 2 plus inches of rain, will likely
fall. Bethel and Dillingham could see over an inch of rain with
this system. Farther east, the stalling front will signal a sharp
cutoff to the precipitation. Thus, locations from Lime Village to
Iliamna may see only trace amounts of rain.

While the trough axis remains over coastal Southwest Alaska
through Thursday, most of the energy from the shortwave drops
south of the Alaska Peninsula. This will help taper off the
precipitation to more of a showery nature for the aforementioned
locations by late Wednesday into Thursday.

Further west, a series of waves will move across the western
Aleutians, over top a North Pacific ridge. The first of these
will bring rain and westerly winds to the western Aleutians for
Tuesday. The second, associated with a warm front attached to a
Kamchatka Low, will move over the region Tuesday night through
Wednesday. These two waves will bring nearly constant rain for
Shemya to Adak and Atka, where 1.5" to 2" of rain could fall
through midweek.

-TM

&&

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

The weather pattern across Southern Alaska will continue to go
catawampus through the long-term period. This is to say that a
large Bering Sea low with numerous fronts pivoting around it will
keep the mainland region wet, cooler, and unsettled. Areas of
moderate rain, potentially heavy at times, will impact mainland
Southwestern Alaska, the Alaska Peninsula (AKPEN), and Kodiak
Island Friday and Saturday. Moderate rain makes it to the Eastern
Kenai Peninsula, Prince William Sound, and the Northern Gulf Coast
Friday evening. Rain will continue into Saturday night for those
areas with favorable upslope southerly to southeasterly flow.
There are still questions with how much precipitation makes it
inland over the mountain ranges. Scattered light precipitation is
certainly within the realm of possibility as the system look
pretty moist. The Bering Sea low will then move eastward into the
Gulf of Alaska for Sunday. This will help deliver the Northern
Gulf Coast and Prince William Sound another round of steady rain
for Sunday into Monday. There is uncertainty in how far inland
these rains will make it into Southcentral. However, in general,
the weather pattern also looks active beyond Monday across
Southcentral.


.AVIATION...

PANC...MVFR or low VFR ceilings will persist through this
afternoon and into this evening. A weak Turnagain Arm wind will
persist over the terminal through Monday evening.

CCC

&&


$$