229
FXAK68 PAFC 241211
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
411 AM AKDT Sat May 24 2025

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

A series of upper-level waves and advection of vorticity lobes
across the Copper River Basin will help drive diurnal showers and
isolated thunderstorms through the Memorial Day weekend. The first
first of these waves has moved into the Northern Gulf overnight
with a bands of moderate to heavy rain showers now south of
Seward. A second wave, distinctly visible in water vapor satellite
imagery, is moving over the Chugach Mountains from the Copper
Valley, as of 4 AM. Showers redeveloped over the central Chugach
overnight due to persistent instability and lift due to this
feature.

Another vorticity lobe will advect southwest across the Copper
River Basin today, out ahead of an inverted upper-level trough
moving from the Alaska Panhandle toward Kayak Island. Much like
yesterday, the advection of increasing vorticity over the Copper
River Basin will provide enough lift and instability to kick off
another round of showers and isolated thunderstorms for the
region. Showers and isolated thunderstorms will also be possible
along the western facing foothills of the Chugach and Kenai
Mountains this afternoon and evening as the flow aloft weakens and
becomes slightly southwesterly ahead of the aforementioned wave,
allowing for low-level convergence along the mountains.

This scenario repeats for Sunday afternoon and evening as the
upper-level trough sweeps over the Copper Valley and into Prince
William Sound. Again, increased vorticity and moisture with this
feature will increase lift and instability over the Chugach and
Kenai Mountains. A developing southeasterly flow may allow any
showers and thunderstorms to move from the mountains over valley
locations, including the Western Kenai and Anchorage Bowl. The one
mitigating factor will be the extent of higher clouds over
Southcentral.

Expect another round of gusty sea breezes for coastal communities
this afternoon. Sea breezes will keep daytime highs along the
coast in the 50s; however, farther inland daytime temperatures are
expected to be quite similar to what was observed yesterday, with
widespread 60s for valley locations. For Anchorage, yesterday
marked the first official 60 degree day this season.

For Sunday, southeasterly gap winds will return for Turnagain Arm
and the Knik and Copper river Valleys as a coastal ridge builds
out ahead of an area of low pressure moving northwest from the
eastern Gulf. Also on Sunday heading into Monday, a front
approaches Kodiak Island from the Aleutians bringing rain and
stronger easterly winds for the island.

-TM/AM

&&


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

For Southwest Alaska, partly cloudy skies under generally weak
flow allows temperatures to climb into the low 60s today. Slightly
cooler temperatures are expected Sunday as flow shifts to
offshore with a front approaching the coast. The resulting
instability will support scattered rain showers across much of the
Southwest mainland during the afternoon and evening hours through
the weekend.

Further west, a gale force front and associated low continue
tracking across the Bering Sea. Rounds of rain showers and
increased winds move west to east across the Aleutians towards the
Alaska Peninsula through this weekend, with the primary area for
gales today being the Western Aleutians. Cooler air filters in on
the back side of the low allowing gale force winds to continue
across the Western Aleutians through Sunday morning, with
northerly winds below gale force spreading across the Bering
Sea/Aleutians for Sunday and Monday.

&&


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

The broad and persistent upper level low anchored in the Gulf of
Alaska for next week looks to bring unsettled weather across the
southern portions of the state with moist onshore flow. While
periods of precipitation will be possible throughout next week for
Prince William Sound and along the Gulf coast, the heaviest and
most prolonged rainfall is expected to remain mainly centered over
southeast Alaska as multiple shortwaves rotate through the
pattern. Model agreement remains fair through the middle of the
week with a reinforcing shortwave in the North Pacific merging
with the system in the Gulf, followed by an Arctic trough digging
south into the Bering as favored by ensemble guidance.

Further inland, a weak upper level ridge axis looks to set up
across the Interior, promoting scattered afternoon and evening
showers. Isolated thunderstorm development will be possible in the
presence of an unstable airmass, particularly through the first
half of the period. The long term wraps up with a Kamchatka low
merging with a North Pacific shortwave and entering the western
Bering, bringing another round of active weather for the Aleutian
Chain.

-JH

&&

.AVIATION...

PANC...VFR conditions are anticipated through the TAF period.
Southerly flow will shift southwesterly as a sea breeze develops
this afternoon. Gusts up to 15 to 20 knots are expected in the
evening hours before diminishing overnight. A more robust coastal
ridge developing will lead to enhanced Turnagain Arm winds by
Sunday afternoon.


$$