Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 061358
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
458 AM AKST Tue Dec 6 2016

.ANALYSIS AND UPPER LEVELS...
The closed upper level high pressure remains parked over the North
Slope with a ridge extending from the Eastern Siberian area
southward through the central Bering/Aleutians into the North
Pacific Ocean this morning. Meanwhile, a trough is dropping down
from the north into the Tanana Valley region, and a closed low is
positioned over the Anvik area. While in the Gulf a 1012 mb low
is located just east of Kodiak Island resulting in a showery
weather regime. The bulk of the precipitation is staying along the
northern coastal communities as this system tracks farther
northward. The radar imagery has the showery echoes moving onshore
in the northern gulf, and precipitation spilling over the Kenai
into the Cook Inlet, and the lower Susitna Valley. While the
Southwest Alaska region is on the backside of this synoptic
system. Therefore, they are receiving northwesterly winds
accompanied by cooler temperatures with light snow showers in the
Bristol Bay interior this morning.

&&

.MODEL DISCUSSION...
The models continue in good agreement with the GFS/NAM being the
preferred models of choice with the low pressure system tracking
into the northern Gulf. While the central/northern Bering is being
dominated by high pressure. Farther west a low is tracking into
the Kamchatka Peninsula with the associated weather front
tracking through the western Bering/Aleutians this morning. The
forecast is average heading into the midweek.

&&

.AVIATION...
PANC...The ceilings should remain around 5000 ft as precipitation
spills over from east to west over the Chugach Mountains with the
low pressure located in the northern Gulf this morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The low over the Gulf of Alaska will slowly drift east today and
then slowly south tonight through Wednesday night. At the upper
levels a "Rex block" is trying to form, with a ridge over
northern and central alaska, and the low over the gulf. Showers
will rotate around the Gulf low, mainly into the coastal areas.
For inland areas, the air mass is fairly dry and the flow still
offshore. This will limit the amount of moisture that could reach
the ground. Some isolated showers may sneak over the mountains
into inland areas, especially in the Copper River basin where the
mid to upper flow is more favorable.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Snow will taper off to showers across coastal portions of Bristol
Bay through the morning hours as the triple point low continues
to push into the Gulf of Alaska. A few flurries may linger into
tonight along the Aleutian Range and Alaska Peninsula as cold
advection takes hold on the backside of the low. Otherwise, a cold
and dry offshore flow pattern similar to late last week will
settle over the southwest mainland for the next several days as
another arctic air mass filters into the region on the backside of
the gulf trough.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Cold advection in northerly flow will keep scattered snow showers
focused along the Bering side of the Alaska Peninsula over the
next fews days, with gusty Small Craft Advisory level winds and
freezing spray impacting the waters of the far southeast Bering
and the south side of the Akpen. Meanwhile, benign conditions and
perhaps even some sunny skies will be found over the central
Bering through the middle of the week beneath a stout upper level
ridge. A storm force front will move over the far western
Aleutians tonight accompanied by possibly heavy rain. This feature
will fail to make much eastward progress through Wednesday as it
encounters the ridge to the east and the parent low moves into
eastern Russia, keeping the bulk of the impacts confined to the
western Bering.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The first few days of the long term forecast will be characterized
by widespread middle, and high clouds inland with snow showers
along the north Gulf coast. The greatest concentration of snow
showers will be in the Western Prince William Sound area. Inland
areas will likely only see flurries if anything.

A weakening upper-level low pressure will be spinning in the Gulf
at the onset of the forecast. Showers in the Gulf will be forced
by waves rotating around the upper low as well as unstable low-
level flow, and orographic upslope on the eastern Kenai Peninsula.
A more substantial disturbance comes across the Gulf on Thursday
in the form of an inverted trough. Details of this disturbance are
not well agreed upon, but it does look like a likely short period
of snow for the north Gulf coast; more uncertainty inland.

The extended forecast (Friday-Tuesday) will be very similar to
current conditions; gusty winds along the north gulf coast will be
accompanied by cold, dry arctic air from the interior. The same
developing blocking high will stay anchored over northwest Alaska
keeping a steady offshore flow of reinforcing arctic air over the
mainland.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory Thompson Pass...131.
MARINE...Storm Warning...178.
         Gale Warning...127 130 177.
         Heavy Freezing Spray Warning...160 180 181.

&&

$$

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



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