Small Craft Advisory 289, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
537 AM AKDT Fri Apr 6 2018

.ANALYSIS AND UPPER LEVELS...
Three upper level lows are circulating about the forecast area
this morning. The low pressure center that brought snow across
much of the southern mainland during the last several days is now
slowly spinning over the eastern Bering near the Kuskokwim Delta
coast. This low is slowly lifting north, allowing two other low
pressure systems to enter the forecast area. One low is moving
toward the southern Gulf and the other is moving to the Aleutian
Chain.

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.MODEL DISCUSSION...
Models are in good synoptic agreement on the 00Z run on the
slow progressive pattern through the weekend. NAM was the favored
model for the higher resolved details.

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.AVIATION...
PANC...VFR conditions and light northerly winds are expected to
prevail through Saturday morning.

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.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A weak front will pivot up against the north Gulf coast this
afternoon. Expect light rain this afternoon in the western Prince
William Sound area, except snow at higher elevations. The front is
weak, and the antecedent air mass is dry, so precipitation will
have a hard time making it over the terrain into the Cook Inlet
region. However, there is a decent area of isentropic lift and
moisture above mountain top level, so forecast thinking is
sprinkles late this afternoon, changing to flurries this evening
as the low-levels cool back down. A weak outflow pattern sets up
as the front departs on Saturday, but winds won't get as strong as
a wintertime setup. The big story for the weekend will be
temperatures. Cloud-free sky and 850mb temperatures above zero
should yield the warmest temperatures of the year for most areas
of Southcentral Alaska. Solid 40s are a good bet while this
forecaster believes a few places will hit 50 degrees Saturday
and/or Sunday. Spring has sprung.

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.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Friday and
Saturday)...

The stationary area of snow showers across portions of Southwest
Alaska continues to diminish this morning. As expected, there were
widely variable snow totals from this event, with King Salmon
getting over 6 inches of snow. Meanwhile places on either side of
the band, including Dillingham and Iliamna got only some flurries
from time to time. The band is expected to continue very slowly
weakening through the morning, with additional accumulations
likely. Once the sun comes up Friday morning and gets to work
heating the atmosphere, that in combination with diminishing
snowfall rates will end any significant accumulations from midday
onward. Sunny skies will return to most of Southwest Alaska from
King Salmon northward for the weekend. A warming trend will begin
in earnest with the return of the sunshine. Most lower elevation
communities will get above freezing by Saturday, and by Monday,
widespread 40s are expected.

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.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Friday
and Saturday)...

A front moving across the southern Bering and much of the
Aleutians will move north and eastward into the central Bering
Friday, with precipitation expected in the Pribilofs late Friday
afternoon. Meanwhile the eastward progress of the front will
largely be halted along the Aleutians, with most locations from
Unimak Island eastward missing out on additional precipitation
from it. The front will shear apart on Saturday as it remains
stationary just west of Dutch Harbor. The next front moves into
the western Aleutians late Saturday night into Sunday, though it
too will be a slow-mover.

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

Ridging pushing over from the east into mainland Alaska will help
to keep fair conditions for the southern mainland into early next
week. A front associated with a low in the southern Gulf will
push into the northwest coast, bringing precip to the coastal
regions starting on Sunday. Out west, models are in decent
agreement with the placement of a low pressure system near the
western Aleutians early in our forecast period, which will move
into the central Aleutians and diminish by Tuesday night. Models
are uncertain with the placement of a second low moving into the
western Aleutians Tuesday night, meaning that ensembles will be
more helpful in determining the placement. For mid next week the
ensembles show that most of the activity should stay south of the
mainland.

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.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

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SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...ML
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
LONG TERM...AH