Gale Warning 341, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
727 AM AKDT Mon Apr 15 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Today through Wednesday night)...

Just about every location across Southcentral is being treated to
nearly crystal clear skies this morning courtesy of a strong upper
level ridge moving directly overhead. An offshore pressure
gradient is quickly diminishing as flow from the surface to the
upper levels becomes very weak near the crest of the ridge moving
into place. Light winds , very dry dew points in 10s to 20s and clear
skies have allowed temperatures to drop all the way into the upper
10s to low 20s this morning across all but the coastal Prince
William Sound region, so expect a chilly start to the day today.
Temperatures will warm back into the 40s across interior valleys
by this afternoon as much of the region sees another full day of
sunshine.

By this evening, the ridge axis will begin to shift east towards
the AlCan border, allowing flow to strengthen and become
southerly between the ridge to the east and a low moving over the
Bering Sea. This will allow an onshore gradient to develop, with
light gap winds picking up along the Turnagain Arm, Knik Valley
and Copper River Basin by late this afternoon. Cloud cover will
begin to increase as moisture from the Gulf is pulled northward
through Tuesday morning. However, any light rain/snow will be
exclusively focused where winds upslope into terrain along the
eastern Kenai Peninsula and western Prince William Sound through
at least Tuesday afternoon.

Between Tuesday evening and Wednesday morning, a more active
pattern will begin to take shape as attention shifts to a large
North Pacific low that will make slow progress north towards the
AKPen through midweek. This low will advance a strong front and
attendant moisture tap north into the southern and western Gulf,
spreading strong easterly gale force winds with gusts into storm
force range across the southwestern two-thirds of Gulf waters by
Wednesday morning. The bigger impact from this system will be
moderate to locally heavy precipitation rates spreading into
Kodiak Island. Temperatures could be cold enough in the low to mid
levels for initially a rain snow mix to move into Kodiak at sea
level on Tuesday evening, but otherwise steady, moderate rain is
expected to begin around this time and persist well into
Wednesday. Total rainfall amounts of 2 to 4 inches will be
possible across Kodiak Island between Tuesday evening and early
Thursday morning, with potential for rainfall to persist into late
in the week as the front stalls out. Lighter rainfall amounts
generally less than an inch will also be possible along the
eastern Kenai Peninsula during the same timeframe, including near
Whittier and Seward.

Most of the remainder of Southcentral will stay dry but steadily
cloudier through Wednesday night. Strong easterly gap winds will
also develop along the Turnagain Arm Tuesday night and persist
through at least Wednesday night.

-AS

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA, AND ALEUTIAN
ISLANDS (Days 1 through 3: Today through Wednesday night)...

A fully occluded, compact low will continue to trek north across the
Bering Sea today...nearing the Bering Strait by this evening. Storm
force winds have accompanied this system as the associated front
pushes east across the eastern Bering and central Aleutians. Strong
winds, along with moderate snowfall, moved into the Pribilof Islands
overnight with winds gusting 50 to 55 mph and visibility dropping to
a half mile at times. As the front pushes north and east this
morning, conditions will improve across the Pribilofs by mid to late
morning. Temperatures have remained near to just above freezing
resulting in a heavy, wet snow...but may see a transition to a
rain/snow mix before precipitation comes to an end later this
morning.

This system will next impact the Kuskokwim Delta coast and Nunivak
Island later today as it passes just to the west of Nunivak. The
core of strong winds will move into the Kuskokwim Delta with snow
quickly spreading inland with the arrival of the front. As with the
Pribilofs, temperatures look to remain near freezing across
Southwest resulting in a heavy, wet snow. This should help to
minimize resuspended snow concerns, but a period of moderate snow
and winds gusting up to 55 mph will allow for reduced visibilities.
The system will not linger long as it continues to lift towards the
Strait, so only a few inches of snowfall accumulation are
anticipated. The heaviest snowfall will be this afternoon and
evening with improving conditions by late tonight through early
Tuesday morning.

On the heels of the departing system, a Kamchatka low will eject
into the western Bering with an elongated trough associated front
sweeping east across the central Bering Sea and Aleutian Chain
through midweek.

&&

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

An amplified pattern will be in place on Thursday with a longwave
trough stretching from western Alaska to south of the Eastern
Aleutians. Anchored in place, through at least Thursday, will be
a vertically stacked low to the south of the Alaska Peninsula.
Enhanced northerly flow over the Bering with below normal
temperatures are forecast across the Bering into the Central
Aleutians Thursday. Downstream of the trough, southeasterly flow
will bring plentiful moisture into the western Gulf along with
warmer temperatures. Kodiak Island, in particular, will be in the
cross hairs of a potential atmospheric river. With an initial
round of precipitation on Wednesday, renewed and heavier rainfall
will be possible Thursday into Friday as the stacked low south of
the AKPEN remains largely stationary. There is quite a bit of
uncertainty in how far north the front and steady precipitation
will make it. Portions of the Kenai Peninsula and Prince William
Sound could see a period of steady precipitation (primarily in the
form of rain at sea level) mid to late week, or it could stay
mostly dry if the front stalls to the south. Details to resolve
over the coming days will be how far south and west the low moves
while south of the AKPEN. The deterministic GFS continues to trend
well west of ensemble guidance, which could change the location
of the atmospheric river entirely by the middle of next week, and
will certainly have implications on precipitation chances for
Kodiak as well as the Gulf coast.

BL

.AVIATION...

PANC...VFR conditions will continue today. Turnagain Arm winds
will pick up later this afternoon and evening hours.

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1000 AM AKDT Mon Apr 15 2024

AKZ155-160700-
Kuskokwim Delta-
Including the cities of Bethel and Nunivak Island
1000 AM AKDT Mon Apr 15 2024

...ELEVATED WATER LEVELS POSSIBLE FOR THE KUSKOKWIM DELTA AND
KUSKOKWIM BAY THROUGH MONDAY EVENING...

Gale force southerly winds with gusts to 55 mph will continue
along the Kuskokwim Delta coast through this evening as a surface
low moves north from the Pribilof Islands to north of Saint
Lawrence Island. This will bring the potential for elevated water
levels of 2 to 4 feet above the normal highest tide line.

Although there is extensive areal ice coverage along the coast,
there is still the potential for water to move on top of ice and
push onshore in areas free of ice. Trails that cross the ice along
the coast may become covered in water. Ice could also push onto
the coast, especially along south and west facing coastlines.

Residents along the coast should monitor conditions for potential
impacts and stay tuned to the latest forecast updates at
www.weather.gov/afc