Small Craft Advisory 961, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
526 AM AKST Sun Dec 4 2016

.ANALYSIS AND UPPER LEVELS...
A low over the Gulf is creating enough of a pressure gradient for
outflow winds to continue for Southcentral Alaska. Ridging along
the west coast is also helping to aid in the northerly flow over
the southern mainland. With the cold air advection over the
southern mainland over the last day there is now an abundance of
cold air settling in over most of Southcentral Alaska. Out west, a
front is pushing through the central Bering and Central Aleutians
bringing up enough warm air to see some rain.

&&

.MODEL DISCUSSION...
The models are in decent agreement into the mid term but there
have been issues with a low in the eastern Bering Monday as it
tracks towards the Gulf. However, the 00Z and now 06Z runs are
getting into better agreement with the low track.

&&

.AVIATION...
PANC...Winds will diminish throughout the morning as upper level
support weakens. Otherwise, conditions will be VFR with light
northerly winds by mid afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The low that has been over the Gulf of Alaska will move southeast
today and then out of the Gulf tonight. As a result the strong
offshore winds will weaken. Cloud cover will diminish as high
pressure aloft builds over south central Alaska. The clear skies
and very cold air mass will allow strong radiative cooling
tonight, producing the coldest temperatures of the year so far at
most locations. A low pressure system moving in from the west on
Monday will bring precipitation to Kodiak Island by the
afternoon. This should start as snow, possibly changing to rain on
the south end of island by late Monday night. Precipitation will
push to the north Gulf coast Monday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
One more day of clear and cold conditions is in store for the
southwest mainland beneath high amplitude ridging before an
approaching system brings increased cloud cover and the potential
for precipitation to the area late tonight into Monday. The
Kuskokwim Delta will be the first region to see the impacts of
this system late tonight as the front currently over the Bering
Sea slowly approaches the coast while a triple point low takes
shape to the north of Cold Bay. This feature will then move
eastward across Bristol Bay on Monday before moving into the Gulf
of Alaska Monday night, bringing light overrunning snowfall to
Bristol Bay and perhaps portions of the Delta and the Lower
Kuskokwim Valley. Precipitation will begin to taper off once again
by Monday night as the low departs towards the gulf, bringing a
return of drier northerly flow heading into the middle of the
week.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The primary forecast concerns through Monday will be largely
confined to the southeast Bering as the strong gale force front
moves eastward from the Pribilof Islands to the Eastern Aleutians
and the Alaska Peninsula later today, with the aforementioned
triple point forming late tonight and pushing through Bristol Bay
on Monday. This will keep a strong South-Southeast winds and a
rain/snow mix over much of the region through Monday, with the
developing triple point then helping to focus stronger northwest
winds over the Akpen on Monday night as cold advection commences
on the backside of the low. This will also facilitate a change
back to snow as the predominant precipitation type as the event
begins to wind down. The next front will then enter the far
western Aleutians Monday night accompanied by more southerly winds
and potentially heavy precipitation.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The upper levels are depicting an amplified ridge building over
the Seward Peninsula extending northward into the Beaufort Sea,
and extending southward through the central Bering/Aleutians by
Tuesday. While the Lower Kuskokwim Valley through the Copper River
Basin has a trough swinging through from the north. Therefore,
look for a snow showery regime accompanied by cooler temperatures
filtering into the Southwest Alaska region, and the northern
Alaska Range. This ridge of high pressure further amplifies, and
builds westward through the northern Bering into the Beaufort Sea.
This results in high pressure dominating the Southwest/Southcentral
region through Thursday. The temperatures will below average
through the midweek for the aforementioned regions. Meanwhile, the
Gulf has weak low pressure system entering the eastern Gulf by
Tuesday bringing a showery regime from Kodiak Island northward
into the northern coastal communities before the systems dissipating
by Thursday. By Wednesday there is uncertainty with the possibility
of an upper level shortwave moving through the Tanana Valley
region southward into the Anchorage Bowl as we head into Thursday
time-frame. Meanwhile, a storm force low tracks along the Kamchatka
Peninsula with an associated weather front moving through the
Western Aleutians. This system tracks northward as the weather
front moves into the central Bering/Aleutians, but falls apart as
it runs into the high pressure ridge over the Bering. This
synoptic feature brings southerly gale force winds with warmer
temperatures before being modified with cooler westerly winds on
the backside of this low pressure system.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory 141 145.
MARINE...Storm Warning 185.
  Gale Warning 127 128 130 131 132 150 170 172 173 174 179 180
181.
  Heavy Frz Spray 121 126 127 129 130 139 140 160 181.

&&

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...DEK