Small Craft Advisory 298, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
402 PM AKDT Sat Apr 8 2017

.ANALYSIS AND UPPER LEVELS...

We have an upper level low that continues to weaken while
remaining nearly stationary south of Chignik that is rotating
moisture across the North Gulf Coast. An upper level trough that
resulted in a band of snow overnight has dropped south through the
Kuskokwim Delta and will collide with the moisture advecting
across the Aleutian Mountains this evening. A large fall like
upper level and surface low is rapidly moving east along the
Aleutian Islands. The associated front has pushed into the western
Bering Sea and is sweeping across the Aleutians. Between this
large Aleutian Low and the low south of Chignik is a weak ridge of
high pressure.

Over the Cook Inlet to Susitna Valley region is a moderately
unstable airmass. While not as unstable as yesterday, showery
conditions have already begun to develop today as evidenced by the
latest satellite imagery and radar returns. As mentioned in the
previous discussion this morning, dry air in the lower levels and
a capping inversion around the 500 mb level is inhibiting
thunderstorm potential.

&&

.MODEL DISCUSSION...

The models are in agreement in the near term though diverge as we
move into Monday with respect to the low moving into the Gulf of
Alaska. The sensible difference in the weather is significant as
wind across the northern Gulf of Alaska and along the North Gulf
Coast are much weaker for all models except the GFS. Since the GFS
is the outlier we are continuing along with the same solution we
went with last night. This will bear watching and we may need to
increase the magnitude of the wind in the Gulf of Alaska and along
the North Gulf Coast depending on the model trend.

For the Bering Sea low the models are in excellent agreement.

&&

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

Sunny mornings will be followed by increasing clouds with a few
afternoon and evening showers across the region through Tue.
Clouds will then diminish during the evening and radiational
cooling will allow temperatures to fall into the 20s. Afternoon
highs will rise into the mid 40s at lower elevations with mid 30s
in the foothills.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
An upper shortwave over the Upper Kuskokwim Valley will continue
drop down from the north as it swings through the Kuskokwim
Delta, and the Lower Kuskokwim Valley. This will produce some
scattered snow/rain showers through Sunday. Meanwhile, the low
pressure system located near the southern end of Kodiak Island
remains almost stationary. This system continues to have moisture
spreading westward spilling over into the Alaska Peninsula, and
the Bristol Bay interior through Sunday morning. By Sunday
afternoon a weather front swings by the Eastern Aleutians
resulting in warmer temperatures with chance for rain spreading
briefly into the lower Alaska Peninsula.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
The Western Aleutians has a 983 mb low pressure system located
near Shemya with an associated weather front draped through the
western/central Bering extending through the Central Aleutians.
This system is bringing gale force winds in the Bering, and gale
force westerly winds along the Western Aleutians. The temperatures
will be modified and range in the mid to upper 30s resulting in
wintry mix in the aforementioned region. By Sunday afternoon this
system will be located west of Dutch Harbor at 990 mb. The
associated front will cover majority of the Bering and drape
through the Eastern Aleutians. This brings a widespread of
moisture with warmer temperatures, and produces a wintry mix along
the Chain extending into the lower Bering through Sunday.

&&

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

The long term forecast will not be seeing drastic change from the
current forecast solution. The week begins with high pressure over
the eastern mainland effectively blocking the the approaching low
in the Gulf of Alaska and results in the Bering Sea low also just
having a glancing blow at southwest Alaska then moving southeast
to the low complex south of the Gulf of Alaska. The Bering Sea and
Aleutians will remain very active as yet another strong storm
moves in on the heels of the exiting storm and rapidly sweeps
across the Aleutians to the Bering Sea coast by mid week. This low
will then be followed by yet another strong low that will take a
more northern track across the Bering Sea.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales 178 411.

&&

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...SS