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000
FXAK68 PAFC 222352
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
352 PM AKDT Mon Apr 22 2024

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

Increased low-level moisture and weak lift associated with shortwave
troughing over the inland Bristol Bay area has allowed for diurnally
driven cumulus field over the Anchorage Bowl and up through the Mat-
Su Valleys. Some of these may be able to squeeze out some light
precipitation this afternoon before starting to dissipate from loss
of heating. Temperatures this afternoon will be highly dependent on
cloud cover and may jump up several degrees if clouds clear for a
period. Otherwise, expect most locations across the western Kenai,
Anchorage Bowl and Mat-Su Valleys, and the Copper River Basin to see
temperatures generally ranging from the mid 40s to around 50
degrees. Gusty winds through the Turnagain Arm, Knik River Valley,
and Copper River Valley will peak tonight...decreasing through
Tuesday morning.

For the western Kenai and most of inland Southcentral, mild
temperatures and benign weather will continue through at least
midweek. Isolated to scattered showers may linger into tonight, but
should dissipate by Tuesday morning as the shortwave trough over
Bristol Bay moves eastwards towards the Copper Basin overnight.
Ridging will then build over Southcentral and continue to amplify
Tuesday into Wednesday.

For Kodiak, Prince William Sound, and the Gulf coastal areas...
Scattered to widespread showers will be common the remainder of
today and gradually wind down through the day Tuesday as the
shortwave trough pushes to the east and the low in the central Gulf
treks easts towards Southeast Alaska. Showers will begin to pick
back up along Kodiak by Wednesday as front lifts north across the
AKPen and western Gulf.

- PP

&&


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

A vertically stacked low, roughly 40 nm northeast of Shemya, will
peak in intensity later tonight at around 968 mb. Recent ASCAT
pass shows widespread northeasterly gales west of Saint Matthew
Island, extending to just north of Shemya. The low is expected to
meander almost due north the next 48 hours, ending up almost 300
nautical miles northwest of the Pribilof Islands. The most
pressing concern across the Bering and Southwest Alaska will
involve expected gusty conditions associated with the low as it
tracks just north of the Central Aleutians and its front slides
through the Pribilof Islands, eventually spreading into the
Kuskokwim Delta coast.

Latest observations in Saint Paul show east to southeasterly
gusts up to 45 knots and increasing rain showers as the front
moves overhead. Winds over the Pribs have likely peaked intensity
and should trend down through midnight tonight. Further south
along the front, the Eastern Aleutians are also seeing an uptick
in precipitation. Winds through Dutch Harbor are gusting up to 35
knots. These gusty conditions will be the norm along the front as
it continues east, spanning Nunivak Island tonight. An initial mix
of rain and snow across Mekoryuk should transition to all rain
through tomorrow morning as temperatures warm to above freezing
and winds gust to around 40 mph. As a result, the threat for any
blowing snow will be relatively low.

The more potent portion of the Bering Sea low will be further
south and west over the Western and Central Aleutians. Winds
wrapping around the backside of the low and spreading
northeastward ahead of the low will bring widespread gales and
gusts to 50+ knots tonight through Tuesday morning. Peak forecast
wind gusts across Adak will top out at around 65 mph through early
Tuesday morning. However, the stacked low should be steadily
weakening by that point and southwesterly gusts associated with
the front moving into the Eastern Aleutians will likely trend
below gale force by tomorrow evening.

Finally, while Southwest Alaska is expected to see mostly benign
conditions the next days, showers, mostly rain, begin to spread
inland of the coast on Wednesday.


&&


.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 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...Low stratus in place earlier this morning has broken up,
and VFR conditions should generally persist through this evening.
A stray rain shower or two could impact the terminal this
afternoon, but even this activity would not bring more than
briefly MVFR conditions. There will be some chance for low
stratus to fill back in over the Mat Valley later tonight and
drift back down into Anchorage, possibly bringing a return to MVFR
or lower ceilings. However, this potential is uncertain and will
depend on whether mid to upper level cloud cover can clear out
later tonight.

&&


$$