652
FXAK68 PAFC 201318
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
518 AM AKDT Mon May 20 2024

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

A vigorous upper level low currently over the Copper River Basin
is producing rain and snow this morning with snow on many webcams
in the area. The snow is sticking on grassy surfaces and trees in
most locations, however Mentasta Pass webcam is showing slushy
accumulations on road surfaces. Partly cloudy to mostly cloudy
conditions along with light winds are found over most of
Southcentral. The rain and snow in the Copper River Basin will
diminish this afternoon.

A weak shortwave moving north and east today over the Western Gulf
of Alaska will bring increasing chances for rain over Kodiak
Island this afternoon and evening, and over the Kenai Peninsula
this evening. A stronger front that is wrapping around a low in
the Eastern Bering Sea will push north and east over Southcentral
on Tuesday. This front will bring periods of rain and higher
elevation snow to Southcentral. Southwesterly flow aloft is
expected to allow the Anchorage Bowl to get some rainfall Tuesday
afternoon, but a switch in flow to a southeasterly direction on
Wednesday will cause downslope drying to occur over the area. A
ridge over the Northern Gulf of Alaska and Copper River Basin
will help build a pressure gradient over the Chugach and Kenai
Mountains as the front approaches from the southwest, which will
result in stronger southerly gap winds taking place Tuesday
afternoon near the Kamishak Gap, Turnagain and Kink Arms, and the
Copper River Basin. This next system will result in a brief cool
down over the entire region, but should quickly rebound to closer
to normal temperatures later in the week.

-CC

&&

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

Satellite imagery shows a cloudy start to the work week, with
widespread clouds around a Western Bering low and its front, which
currently extends across the Pribilof islands and towards the
Eastern Aleutians and Alaska Peninsula. Patches of clear sky are
visible over Southwest Alaska ahead of this front, though fog and
low stratus are slowly spreading over parts of the Bristol Bay
coastline early this morning.

The Western Bering low and its front will be the main weather
makers through Tuesday, with much of the impacts (though lower-
end) centered over Southwest Alaska. The front reaches Southwest
Alaska this afternoon/evening, bringing with it light rain and
breezy southeasterly winds. A strong upper level shortwave
rotating around the low will help reinvigorate the front early
Tuesday morning, leading to moderate rain rates before the front
exits into Southcentral Alaska Tuesday afternoon and evening.
Rainfall totals from this afternoon through Tuesday afternoon will
be around 0.5 to 0.75 inches for Bristol Bay and Lower Kuskokwim
Valley, with about 0.25 to 0.5 inches for Kuskokwim Delta and
Nunivak island. About 0.1 inches or less are expected for Alaska
Peninsula. Overall forecast confidence is relatively high for this
front, with only minor uncertainty regarding precipitation timing
and maximum gusts expected through Kamishak Gap.

Behind the front, expect an influx of colder air aloft,
breezy conditions, and widespread showers as another upper low
merges with the Bering Sea low later today. This influx of colder
air could bring the potential for snow showers to mix in with rain
showers. By Tuesday, a ridge moving in from the west will bring a
brief spell of calmer conditions as it moves across the Bering Sea
and Aleutians. Behind it, however, a Kamchatka low will begin
pushing its front into the Western Bering and Aleutians for
Tuesday evening. This incoming storm does look to be a little
stronger than our present one, with the potential for localized
areas of gale force winds, as well as the potential for moderate
to heavy rainfall along the front.

-KC

&&

.LONG TERM FORECAST (Days 4 through 7)...

Thursday, an upper-level low centered over the Bering begins to
elongate southeastward into the Gulf. Surface precipitation may
start as snow then transition to rain for the Western Capes,
Kuskokwim Delta, and Nunivak Island. A brief ridge forms before
the next upper-level low consolidates and moves eastward from Attu
Island. By Friday the new low has transited the Bering and
continued across Southwest Alaska into the Gulf by Sunday. The
highest rain amounts are expected along the Kenai Peninsula and
the northern Gulf coast. High pressure builds behind this low
across the Bering Saturday and Sunday.

&&

.AVIATION...

PANC...VFR conditions are anticipated through the TAF period. A
mild Turnagain Arm wind may develop this afternoon with the
majority of winds remaining over Cook Inlet and away from the
terminal. A better chance for increasing southeasterly winds
develops Tuesday morning as an approaching trough and front
tighten the pressure gradient over PANC with potential gusts above
15 knots.

-BL

&&


$$