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000
FXAK68 PAFC 190034
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
434 PM AKDT Thu Apr 18 2024

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

Wet and windy weather persists into the weekend as an atmospheric
river lingers near southern Kenai Peninsula and Kodiak Island. A
Flood Watch is in effect for Kodiak Island, while a Flood Advisory
is in effect for the Kodiak City area. We continue to monitor rain
amounts and intensity associated with the atmospheric river. Aside
from an increase in precipitation amounts for Kodiak Island, few
major changes were made with this most recent forecast package.

Diving into the details... an Omega block is in place over Alaska
and Canada, with a high amplitude ridge centered over NW Canada,
a deep trough and closed low nearly stationary to the south of the
Alaska Peninsula and Kodiak Island, and a deep trough and low
east of the ridge over the heart of Canada. An atmospheric river
extends from the East Tropical Pacific north and west to Kodiak
Island and the western Gulf of Alaska. A series of upper level
waves rounding the upper low are tracking westward across the Gulf
to Kodiak Island, bringing a resurgence of stronger winds and
precipitation from this afternoon through late tonight.

The upper level ridge strengthens over Southcentral through
tomorrow, keeping rain limited to areas south of Seward.
Meanwhile, steady rain will continue for Kodiak Island, with
periods of moderate to heavy rain as upper level short-waves
continue to pass overhead. There has been some uncertainty with
rain amounts as the atmospheric river oscillates north and south
under the influence of these shortwaves. With models keeping the
front more consistently over Kodiak Island, have increased rain
amounts and durations. The heaviest periods of rainfall will
likely occur this afternoon/evening, and from early Friday morning
through the afternoon. Expect lighter but steady rainfall
throughout for Kodiak Island, bringing an additional 2-3 inches of
rain from what has already been observed yesterday and today.
Rain lingers for Kodiak Island through Saturday, though
precipitation should be much lighter as the surface low occludes
and the tropical moisture tap is lost.

-SEB/KC

&&


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

A vertically stacked low remains roughly 300 miles to the south
of Sand Point and the Alaska Peninsula this evening. An axis of
cooler temperatures aloft (-10 degrees Celsius at 850 mb)
stretches from the north central Bering down through the Eastern
Aleutians as flow wraps cyclonically into the southern side of the
low. Wind remains elevated within this thermal gradient with a
swath of northerly gales extending from east of the Pribilof
Islands down into the Dutch Harbor and Akutan. Ongoing snow
showers across Unalaska have kept visibility between one half mile
and one mile, as winds gusting over 30 knots are resulting in
poor visibility within the falling snow. Temperatures are likely
too warm at the surface for snow on the ground to blow around, but
reduced visibility and deteriorated conditions are forecast to
persist through Friday morning. A winter weather advisory remains
in effect for the Eastern Aleutians through 8am AKDT Friday.
Likewise, a blizzard warning for Toksook Bay has been extended
through 6am AKDT Friday morning as snow and blowing snow with
visibility down to one quarter mile are expected to linger through
tonight. Of note, rain has been observed in Bethel with surface
temperatures below freezing. Thus, a mix of freezing rain and snow
is possible into tonight with light icing on surfaces.

East of the stacked low, strong southeasterly flow is spilling
into the Kamishak Gap. Easterly winds have gusted to around 35 mph
through much of the day for Iliamna, Koliganek, and New Stuyahok.
Winds across all of Southwest Alaska look to remain elevated
through late Saturday. Above normal temperatures are forecast for
the region with mostly dry conditions forecast for Friday and
Saturday. The pattern finally begins to change over the weekend as
the vertically stacked low south of the AKPEN falls apart and a
new developing low moves into the western Bering by Sunday.

-BL

&&


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

Changes are expected as the weather pattern is becoming more
stable conditions through the forecast period. An upper level
ridge is slowly losing its hold across Mainland Alaska. A Western
Gulf of Alaska low weakens and slips across the Gulf to Haida
Gwaii by Wednesday before dissipating. A well developed Aleutian
low maintains some additional upper level support from both
Siberia and and the Northern Pacific through midweek. A number of
moderate shortwaves rotate through the pattern across the
Aleutians and along the Western Coasts.

Periods of rain spread across Southcentral Alaska through
Wednesday from the Kenai Peninsula to the Canadian Border. The
most active weather will be associated with the Aleutian/Bering
low and its front on Monday. Heavy rains spread across the Central
and Eastern Aleutians, with mixed rain and snow over the Bering
with the low center. Gusty Southerly winds move with the front
from the North Pacific, across the Pribilofs and St Matthew
Island. Rain continues to spread into the Alaska Peninsula with
the front through Tuesday, and into Southwest Alaska late Tuesday
and Wednesday. Another round of locally heavy rains moves into
Kodiak Island late Tuesday through Thursday. Gusty Southeasterly
winds moves through the Barren Island into Kamishak Bay Wednesday
and Thursday.

Kutz

$$

.AVIATION...

PANC...VFR conditions will persist. The Turnagain Arm wind is
expected to continue bending southward down Cook Inlet while
generally northerly winds persist over the airport. Southeasterly
winds are flowing across the mountains and generating mountain
waves. Low level wind shear concerns are borderline for the
forecast period with a majority of the shear to remain near or
above the 2000 foot level. At the surface, winds are coming from
the northwest over the terminal and although there is a small
chance for winds to mix and become gusty this afternoon, winds are
expected to remain lighter.

rux

&&

$$