Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 281245

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 AM AKDT SAT MAY 28 2016


A mid-level cut-off high continues to encompass the Alaska
mainland, and is centered over Unalakleet. With broad northerly
mid-level offshore flow occurring across Southcentral Alaska, a
lee trough has formed just inland along the North Gulf Coast and
is pushing toward the northern Gulf. To the south of this
boundary, which includes the vast majority of North Gulf Coast
locations and points south, a light onshore flow has developed
that has resulted in widespread low stratus and fog overnight.
Outside of the coastal clouds and fog, mostly clear skies dominate
much of the southern part of the state.

Out west, a weather front is currently pushing into the Western
Aleutians that will move into the western Bering and Central
Aleutians through tonight before washing out. Another weak low and
associated front southwest of Dutch Harbor is pushing slowly west
toward the Central Aleutians.



Models are in better agreement today on the southwest progression
of an upper level wave into the eastern mainland of Alaska
today into Sunday. However, there is still a lot of difference in
how quickly it progresses westward. This will play a significant
role in the evolution of fire weather hazards and the potential
location and timing of possible thunderstorms as we progress
through the remainder of the long holiday weekend.



The southern progression of an upper level wave, and diurnal
forcing of a thermal trough will help to increase winds across
both the Susitna and Matanuska Valleys Saturday evening. There is
uncertainty in the intensity of these winds as well as the timing
as to whether these winds will coincide with peak diurnal heating.
Sunday looks more promising with stronger winds as the upper level
northerly jet moves into a more favorable position. For Southwest
Alaska, confidence is fairly high in reaching Red Flag conditions
for inland areas of the Kuskokwim Delta and Middle Kuskokwim
Valley. However, any future warnings issued for these Southwest
locations will be contingent on whether fuels are deemed to be
burnable or not.



An upper level high over Western Alaska and a trough over Western
Canada continues northerly flow across much of Southcentral
Alaska today. Northerly gap flows continue across the Copper
River Basin and over the Susitna Valley through Sunday afternoon.
Temperatures across the region are expected to be fairly warm
again today with many inland areas in the 70s. The Susitna Valley
will likely be pushing 80 degrees in a few spots. Cooler air
spreads East across the Copper River Basin Sunday with an upper
disturbance and increased cloud cover and should tend to damper
inland temps. However, inland areas West of the Copper River Basin
will have afternoon highs in the 70s. Cooler temperatures are
expected along the coasts with afternoon and evening sea breezes
through Sunday.

The upper short wave undercutting the mainland ridge on Sunday
will spread shower activity across much of Southcentral by Sunday
evening. Thunderstorm potential will also spread west with the
Copper River Basin and Talkeetna mountains the favored locations

Ridging over the southwest will continue to bring sunny skies with
warming temperatures through this weekend, especially to interior
areas along the Kuskokwim River. Along with dry conditions, subsidence
from this ridge will prevent any showers from forming throughout
the region until this afternoon/evening when they should begin to
develop along the Alaska Range. These showers will then redevelop,
and may even strengthen enough to bring some lightning strikes to
the Alaska/Aleutian ranges Sunday afternoon/evening. For the rest
of the area, conditions will remain dry with some of the warmest
air of the season as temperatures rise well into the 70s. Offshore
flow will also develop on Saturday as the ridge axis slides to the
north, bringing gusty winds to the area during the afternoon and
evening hours on Saturday and Sunday.



The weather throughout the region will remain fairly quiet through
the weekend. A series of upper level disturbances moving through
the Aleutians will bring rains through Saturday morning before
dissipating over the North Pacific, but with winds remaining below
small craft. A stronger and more organized North Pacific low will
clip the Western Aleutians Sunday evening, then move into the
Central Aleutians/Bering by early Monday morning. This system is
expected to produce steady rainfall over the area, and bring gale
force gusts to the Central Aleutians/Bering Sunday night into
Monday morning.


.LONG TERM FORECAST (Days 3 through 7)...

Models are in agreement that a thermal trough draped south of the
Alaska range will make some thunder activity possible. On Monday
the decaying thermal trough drifts west, and the possibility of
thunder continues west of the ranges and then also over the Kenai
peninsula. By Tuesday upper support for convection begins to
weaken as high pressure builds over mainland AK, with only some
shower activity expected through the week.

For the Bering, a low near the central Aleutians will bring at
least small craft or gale-force winds and a chance of rain to the
area Monday night into Tuesday. From that point models begin to
diverge and an ensemble WPC solution was used. This moves the low
north of the chain where it slowly weakens through midweek, with
rain becoming less likely through that time.





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