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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
427 am akst Sat Feb 6 2016

Analysis and upper levels...

The regional synoptic pattern continues to remain locked in a
persistent pattern...driven strongly by a Stout North Pacific jet
stream...which is responsible for spinning up powerful lows before
they move into the Gulf. Another one of these such lows is
currently undergoing rapid cyclogenesis south of the Gulf near
40n. This is forming at the eastern end of a rather anomalous
trough over the northcentral Pacific...with a feed of cold Arctic
air originating from Siberia through the western Bering and into
the trough.

Over the Bering...broad cyclonic low level flow continues as the
cold Arctic air remains over the western portion of the Bering. A
mesoscale low along a diffuse baroclinic zone is tracking into the
eastern Aleutians near Dutch Harbor...with a trough axis/wind
shift moving through southwest Alaska. This feature is spreading
locally moderate to heavy snow along the frontal axis as it moves
inland from the southwest. Near southcentral...a small but dynamic
closed low just northeast of Kodiak is moving toward the Gulf
Coast. This feature will spread rain and snow along the Gulf Coast
and eastern Kenai today and tonight.


Model discussion...

The models are in excellent agreement through the short term
forecast period with the general large scale pattern. They are in
excellent agreement with the large low moving into the Gulf of
Alaska...and are in very good agreement with the powerful bomb
cyclone which will develop southwest of the far western Aleutians
late Sunday and Monday. Forecast confidence is very high.


Short term forecast southcentral Alaska (days 1 and 2)...
the upper level short-wave over the northern Gulf will move inland
today into tonight. Most of the energy with this system will push
into the area surrounding Prince William Sound. Some showers could
be triggered over the areas surrounding Cook Inlet...but probability of precipitation are
fairly low with the limited moisture and dynamics. Upper level
high pressure will build over south central Alaska late tonight
into Sunday. The next front will push into the Gulf from the south
Sunday night. This front is associated with a large low moving
northward...that will be centered about 350 miles south of Kodiak
Island Sunday morning. The front will have a band of storm force
winds that will push across the Gulf. The front will reach the
north Gulf Coast Sunday afternoon and work its way inland Sunday
night and weaken. By late Sunday night the parent low will be
centered just south of Kodiak Island.


Short term forecast southwest Alaska (days 1 and 2)...

Snow over Bristol Bay and the Kuskokwim Delta this morning will
progress inland through the remainder of today and exit into the
western interior by tonight. A period of tranquil weather begins
thereafter with offshore winds increasing as low pressure moves
toward the akpen from the central Pacific.


Short term forecast Bering Sea/Aleutians (days 1 and 2)...
weak low pressure centers will keep an active showery regime over
the Bering/Aleutians and akpen. By Sunday a pair of larger and
stronger low pressure systems will begin to impact parts of the
Aleutians and akpen.

The system approaching the akpen late tonight through Sunday night will
help strengthen northeast winds that will reach storm-force
especially where a barrier jet forms along the south side of the
akpen and Kodiak Island Sunday. This system will bring mainly rain
to the Pacific side of the akpen at least through much of Sunday
into Sunday night.

The second system will move south of the western and central
Aleutians Sunday into Sunday night...bringing snow to the western
Aleutians and a mix of snow and rain for the central Aleutians.
Strong east to northeast winds may also cause some visibility
restrictions due to blowing snow.


Long term forecast (days 3 through 7)...
an active weather pattern will continue across the Gulf and Bering
through next Friday...with drier conditions for inland locations.
Sunday night...low pressure lifts toward Kodiak bringing a reinforcing
wave to the northern Gulf which spreads scattered rain and snow
showers further inland into Monday. At the same time...another low
organizes south of the central Aleutians and tracks eastward
through Tuesday. The surface low associated with this system is
expected to bring a storm force front as it deepens to 950 mb.
This system loses momentum into Wednesday as a ridge builds over
southern Alaska. This ridge currently looks to shunt progress of
this low and another low tracking in from the eastern Beaufort
Sea. This keeps temperature trends above normal in the extended
forecast. Another developing low south of the central Aleutians
spins up and follows a similar pattern as the jet stream remains
nearly zonal along 40n at the end of the next week.


Afc watches/warnings/advisories...
Marine...storm 131 132 138 150 351 352.
Gale 119 120 127 130 136 137 139 155 160 176 177
Heavy freezing spray 185.


Synopsis and model discussion...ja
southwest Alaska/Bering Sea/Aleutians...cirrocumulus

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