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000
FXAK68 PAFC 260039
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
439 PM AKDT Thu Apr 25 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This
afternoon through Sunday afternoon)...

Few changes to the forecast in the near-term. An upper low in the
Bering Sea is poised to pivot towards British Columbia through the
weekend, weakening the fair weather ridge that had been in place
over Mainland Alaska. For today, a shortwave trough moves across
the Mat-Su and Copper River Basin as it transits the western flank
of the ridge. Lift from this shortwave, in combination with
instability due to daytime heating, could lead to scattered
showers in Susitna Valley this evening. Precipitation chances
further increase from tonight through Friday afternoon as the
front currently over Kodiak Island moves north towards Kenai
Peninsula. Overall, not much precipitation is expected for the
Mainland as the front will be weakening as it approaches. The bulk
of this light precipitation will occur along Eastern Kenai
Peninsula, with a small chance for stray showers to move inland.

More active weather arrives by late Friday morning/early Friday
afternoon as a North Pacific low moves towards Kodiak Island and
is enhanced by a shortwave trough rotating around the upper low.
Its associated front will be wetter than what Kodiak Island has
experienced yesterday and today, with forecast rain amounts of
around 1-1.5 inches for Eastern Kodiak Island and less than 1
inch for Western Kodiak Island. This front should remain far
enough south that the Southcentral Mainland will be mostly dry.

Through Saturday, the low near Kodiak Island will descend
southwards, bringing a return to drier and warmer conditions
across Southcentral Alaska as weak high pressure builds in.
Instability due to daytime heating, in addition to shortwave
troughs moving across the Mainland, could lead to convective
showers in the Copper River Basin for Saturday afternoon/evening
and Sunday afternoon/evening. For now, it`s been difficult to hone
in on the showers because the upper level pattern becomes a bit
more disorganized by the weekend, leading to uncertainty regarding
where the upper level shortwaves will go. We`ll be keeping an eye
on these showers and their convective potential as we continue to
update the forecast.

-KC

&&


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

The weather pattern has been somewhat repetitious the past couple
of days with a nearly stationary cutoff low situated west of the
Pribilof Islands. Broad cyclonic flow around the low has promoted
gusty conditions across the western Bering and through the Alaska
Peninsula. A small swath of northwesterly small craft winds
remain immediately north and east of the Central Aleutians this
evening. These winds will push through the Islands of the Four
Mountains and into the Pacific side of Nikolski tonight.
Otherwise, a few areas of light showers are persisting over
Southwest Alaska. Evening radar shows rain over Tuntutuliak and
Bethel as shower activity lifts northward toward the YK Delta.
Additional rain is noted from Koliganek and Lake Iliamna up to
Sleetmute.

The western Bering low is forecast to begin a weakening trend
through Friday morning as it shifts southeastward as an open wave,
to be eventually absorbed by a developing trough over the western
Gulf of Alaska tomorrow afternoon. A gradual decrease in shower
activity is forecast across Southwest Alaska through Saturday
morning as a result. Temperatures over the Bering and Aleutians
will remain at or below normal into the weekend while temperatures
over Southwest Alaska will remain at or above normal.


&&


.LONG TERM FORECAST (Days 4 through 7: Mon through Thu)...

By Monday morning, a familiar ridge over Southcentral will still
be lingering in the area, continuing the clear pattern. An upper
level trough will be situated over the southern Alaska Peninsula,
crossing into the southwestern Gulf of Alaska, and a new upper
level trough entering the western Bering Sea behind it. Through
Tuesday, the ridge will likely extend from Southcentral into
Southwest Alaska following the departure of the AKPen trough,
while the western Bering system pushes a front across the
Aleutians, likely reaching Unalaska by late Tuesday. The front is
expected to generally weaken as it approaches Southwest and the
resident ridge, but the parental low pressure system behind the
front will likely move over the Western and Central Aleutians
through Wednesday.

By Wednesday afternoon, the ridge over southern Alaska may begin
to weaken as the upper-level support shows signs of shifting out
of the area. This may allow for influence from the Bering low to
move into Southwest Alaska and even Southcentral Alaska as the
system approaches by late Thursday. Gauging impacts from this
low in Southwest and Southcentral is still precarious given the
uncertainty regarding the ridge movement, as well as the
location/progression of the low itself. However, given the
prolonged shift towards warmer weather over the next week
expected, impacts from this system will likely not be winter
weather. Although the overall synoptic setup is in fair agreement
for the extended period, the details could mean bigger differences
in the QPF and wind fields across the Bering and Southwest
Alaska.

-CL

$$


.AVIATION...

PANC...VFR conditions will persist. Southeast winds 10 to 15 kts
are expected to develop over the airport late this afternoon into
the evening. Winds are then expected to become light and variable
again overnight.

-CC

&&


$$