Small Craft Advisory 888, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
435 PM AKST Sat Nov 12 2016

.ANALYSIS AND UPPER LEVELS...
A broad upper level low that encompasses much of the eastern
Bering is centered south of the Alaska Peninsula. At the surface,
one main low is centered just south of Sand Point, while a much
weaker low is moving south of the Pribilof islands. A tight
baroclinic zone extends to the west of this low, with broad
northerly flow and convective showers across the western Bering.
Meanwhile, a separate front associated with the low south of
Sand Point stretches all the way to the north Gulf Coast. This
front is bringing gale force gusts to Kodiak Island, and gusty
winds are expected to persist this evening as a coastal jet
extends along the north Gulf coast into the evening hours. &&

.MODEL DISCUSSION...

Model agreement remains well above average for the short term for
both the timing and intensity of the waves rotating around the
low south of the Alaska Peninsula. The NAM is currently best
capturing the intensity of the coastal jet and gap winds due to
its higher resolution. The Canadian remains the main outlier,
indicating greater intensity of the triple point low as it pushes
towards Kodiak Sunday. There is also disagreement among models in
the amount of downsloping that will occur across Anchorage this
evening as the front continues to push northwards.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A front will move inland along the north Gulf coast tonight, with
rain affecting the coast, some snow at higher elevations, and a
slight chance of freezing rain this evening over the Anchorage
Bowl. If freezing rain occurs it will be caused by light rain
spilling over the Chugach into persistent cold air at the surface.

On Sun another low will speed north into the Gulf, with the
associated front again spreading rain to the coast, snow at higher
elevations, and a fairly precipitation-free zone north and west of
the Kenai and Chugach mountains. This will repeat with the third
front on Sun.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
The low south of the Alaska Peninsula will continue to bring warm
southeast flow to the area through Sunday night before it moves
off to the east and ridging builds in from the Bering. The
southeast flow will bring more light precipitation to the area
that will primarily be snow. Some areas in Bristol Bay will be
warm enough for rain. On Sunday night there will also be a chance
for light freezing rain in Bristol Bay as cold air moves into the
area at the surface while warm air moves in aloft. On Monday
ridging will move in which will help to clear out much of the
precipitation but also bring in colder temperatures.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
The warm front moving through the Bering has stalled near the
Pribilof Islands pushing the rain/snow line to that area. Moving
into Sunday the front, and parent low south of the Alaska
Peninsula, will diminish and push off to the east. High pressure
will be moving into the western Bering Sunday and then track
across the Bering into the eastern Bering Tuesday where it will
stall. Behind the high, a new system will move in over the Western
Aleutians Monday and then diminish as it moves to the east.

&&

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

A more progressive pattern is expected Tuesday through Sunday as
an amplification in the longwave pattern is expected. A series of
shortwaves and upper level lows are expected to push off the
Kamchatka Peninsula and move into the Northern Pacific Ocean
through the extended forecast. This will allow the persistent
upper level low over the Gulf of Alaska to finally shift eastward
while a period of unsettled weather moves back into the Bering
Sea. While models struggle quite a bit with low placement and
intensity with a series of lows in the Bering, periods of gale
force winds and heavy rain will be possible; especially over the
western half of the Bering. Southcentral and Southwest Alaska will
be on the calmer side as high pressure over Canada replaces the
broad low pressure over that has persisted for the past week or
so. As the low in the gulf shifts east, the upslope rainfall
observed across the northern gulf coast will come to an end. In
addition, the cold air advection seen over the eastern Bering will
shift across the Alaska mainland and bring a return to near normal
to slightly below normal temperatures for much of Alaska.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Storms 173 and 174. Gales 119 120 130 150 155 165 170 171
172 175 176 179 180 181 185 351 352 412 413 414.

&&

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...MC