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000
FXAK68 PAFC 231306
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
506 AM AKDT Tue Apr 23 2024

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

A short-wave trough extending from the Kuskokwim Valley southeastward
to the Kenai Peninsula and northwestern Gulf of Alaska is stuck
between tow short-wave ridges. The upstream ridge is amplifying
ahead of a large and deep low over the southern Bering Sea.
Anticyclonic flow along the front side of the ridge will overtake
the trough and cause it to weaken as it tracks southward into the
Gulf today. As of early this morning, very light rain associated
with this trough can be found over the northern Gulf, Kenai
Peninsula coast, and Kodiak Island. Radar imagery has shown weak
returns extending across the Kenai Peninsula to Anchorage and the
southern Mat-Su overnight. However, area observations and webcams
indicate that none of this precipitation is reaching the ground.
Considerable cloud cover does extend across all of Southcentral.
In any case, precipitation will taper off today as the trough
weakens, with a few lingering showers across the southern Kenai
Peninsula and Kodiak Island. Breaks of sun will develop this
afternoon and evening, especially inland.

The aforementioned upstream ridge will strengthen over northern
Alaska tonight, then build southeastward toward the Yukon through
Thursday. This will reinforce a weak low level thermal trough
north and east of the Wrangell Mountains. When combined with some
weak upper level short-waves transiting the region both today and
tomorrow, expect scattered showers - especially during the
afternoon and evening hours. While some of the valleys have
started to lose snow cover, the mountains are still completely
covered. Thus, showers will initiate along slopes surrounding the
mountains and any precipitation that falls will be light. The most
likely area to see a few showers is the Tok Cutoff from around
Chistochina northeastward to Mentasta Lake as well as along the
Nabesna Road. The rest of Southcentral can expect a mix of sun and
clouds with continued dry conditions.

A weakening occluded front from the Bering low will approach
Kodiak Island Wednesday, bringing a return to steady light rain.
The front will very slowly progress northward, with rain likely
holding on in Kodiak into Thursday. This is the point at which
model guidance begins to diverge with location and strength of
upper level short-waves, the progression of the front toward
Southcentral, and whether a triple point low will develop in the
Gulf. The Kenai Peninsula will see increasing clouds and a good
chance of rain as the front nears Thursday/Thursday night. It`s
difficult to say whether precipitation ever makes it any further
into Southcentral.

-SEB

&&


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

A 970 mb low lingers in the western/central Bering Sea through at
least tomorrow and will continue weakening through Friday. The
associated front reaches the Southwest Coast this morning,
bringing a round of light precipitation into Southwest Alaska.
There may be a brief shot of snow initially in the Kuskokwim Delta,
however, as temperatures climb above freezing precipitation will
transition to a rain/snow mix or all rain. Light, showery activity
will linger across Southwest Alaska over the next few days.

A second shortwave moves across the Aleutians and Pribilof Islands
today, producing another round of precipitation and winds. This
band is showing a colder profile, particularly aloft, which may
promote brief periods of snow, even with surface temperatures at
or just above freezing for the Pribilofs. However, the main
precipitation type is expected to be a rain/snow mix.

&&


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

On Friday, an upper level low over the Aleutians slides southeastward
into the North Pacific underneath a ridge axis over the Yukon and
mainland Alaska through the weekend. The associated large surface
low also slides southeastward during this time period, continuing
areas of showers and locally heavy precipitation and gusty winds
from the central Aleutians through Southwest Alaska.

As we head into early next week, there is considerable uncertainty
in the upper level pattern over the Bering Sea upstream of the
upper low. The deterministic GFS remains the most progressive,
with a trough entering the Bering and Aleutians Sunday night. The
Canadian and ECMWF, however, begin to build in a ridge over the
Aleutians by late Monday. As such, the GFS brings a moderately
strong low into southwest Alaska, also impacting Southcentral
through Tuesday. There is little to no ensemble support for a
strong low at this time, even with the GEFS. Regardless, there is
still low confidence even within the ensemble systems, with the
GEPS and especially EPS showing a weak progressive ridge building
into Southwest Alaska early next week, while the GEFS still
continues a broad longwave trough across Southwest Alaska early
next week, which could still promote unsettled weather.

-ME

$$

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&


$$