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000
FXAK68 PAFC 212354
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
354 PM AKDT Sun Apr 21 2024

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

Afternoon water vapor imagery is doing a excellent job of showing
mid and upper level features from the western Bering to the western
Canada provinces. From west to east... A large, broad low sits
spinning over the western Bering with several shortwaves rotating
around it. A frontal boundary extends from near St. Lawrence Island
southward through the southern AKPen (near Cold Bay) to a low over
the far southwestern Gulf (south of Kodiak). A shortwave trough is
also lifting north from the southern low and will be moving inland
this evening. The front that has been stalled over the Gulf the past
week is nearing the northern coast. Between the Bering and Gulf
lows, a ridge is starting to amplify with a slug of moisture
advecting north towards the central Aleutians. Near surface features
indicate a surface low moving north over the Kenai and Cook Inlet
and weak surface front near the coast resulting in showers for the
the southern and eastern Kenai, Prince William Sound, and the
northern Gulf coast. Coastal ridge has strengthened today and have
already seen gap flow winds start to increase down into the Copper
River Basin. Should also start to see increasing winds through
Turnagain Arm, and an uptick in the Knik winds, by this evening.
Most of the showers will remain on the Gulf/Prince William Side, but
may see a few light showers or sprinkles make it over the mountains.

The next several days will see continues benign weather with mild
temperatures and slight chances to scattered showers to work up
the Cook Inlet towards the Mat-Su Valley Monday into Tuesday as
the Gulf low splits in two and the northern split lifts into the
AkPen before rotating back south into towards the Kenai Peninsula.
However, the better chances for precipitation will remain on the
eastern side of the Kenai and up into the Prince William Sound.

- PP

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Wednesday)...

An upper-level low in the North Pacific continues to linger south
of the eastern Aleutians, producing shortwaves that will pass over
Bristol Bay through Monday afternoon. The shortwaves will provide
opportunities for showers throughout Southwest before a shortwave
ridge builds over the area on Tuesday. Additionally, a chance of
patchy fog over the southwest coast will be possible tonight.

Our main area of focus over the next few days will be on the
Bering Sea, as our previously-discussed low is getting its act
together north of Shemya. The system will continue to intensify
through Monday afternoon as it slowly moves eastward over the
western Aleutians. In the meantime, the occluded front from the
low will surge eastward toward the central Aleutians and Pribilof
Islands Monday night, producing widespread gale-force winds and
storm-force gusts across the Bering. The front will slowly weaken
as it moves closer to the western Alaska coastline Tuesday into
Wednesday, while the core of the low will still produce gale-force
winds through Tuesday night. With dominant southerly flow along
the front, the main precipitation type will be rain or a
rain/snow mix. The Pribilof Islands will start off as a rain/snow
mix Monday morning before transitioning to rain by the afternoon
and evening. There will be a brief period of snow Monday
night/Tuesday morning as colder air wraps in behind the front.

By Tuesday afternoon, the front finally arrives on the west coast
of Alaska and will linger over the area through Wednesday. The
weakened front will still provide precipitation along the
coastline, with small-craft winds likely around Bristol Bay and
the Kuskokwim Delta. Locations near Bristol Bay and the Alaska
Peninsula will most likely have a rain/snow mix or all rain, while
the Kuskokwim Delta has the best opportunity to remain mostly
snow. Any locations that do receive snowfall will get relatively
low accumulations with this system.

-BS

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through Sunday)...

A front extending across the Gulf from the Alaska Peninsula
across Kodiak Island moves across the Gulf by Saturday. The upper
level ridge over the Alaskan Interior weakens and falls back into
British Columbia by Saturday. This allows a moderately strong low
pressure center to advance from the Central Bering into the
Western Gulf of Alaska by the end of the forecast period. Models
are well clustered early but require the ensemble means to work
out the changes in tracks and strength by late Saturday into
Sunday. The Bering low picks up North Pacific moisture and forms a
front that will extend across the Gulf for Saturday through
Sunday.

Gusty Western Bering surface winds spreads over the Aleutians
through Friday when they move out into the North Pacific. Locally
heavy rainfall associated with a second front connected to the
Bering low spreads over the Aleutians and Bering and Pribilofs
through Friday, and into Southwest Alaska and the AKPEN and into
the Gulf by the weekend. This front continues Eastward, bringing
widespread rainfall over Southcentral Alaska late Saturday into
Sunday. Rainfall is expected to remain nearer the coast, with
higher elevations inland seeing a small amount of new
precipitation. A new frontal system coming out of the Russian Far
East extends its weather over the Western Aleutians and Bering
late Saturday into Sunday.

Kutz

$$

.AVIATION...

PANC...A weak Turnagain Arm wind is expected to increase through
this evening as a weak front lifts north across Southcentral
Alaska. Ceilings will also drop to near 5000 ft through the
evening hours, with a slight chance for light rain to develop
along with brief MVFR ceilings. However, generally expecting weak
downsloping to keep conditions dry and ceilings 3500 ft or above.
Winds diminish overnight and then increase again late Monday
afternoon.

-ME

&&

$$