Small Craft Advisory 194, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
412 PM AKST Sat Mar 4 2017

.ANALYSIS AND UPPER LEVELS...
The pattern continues to hold firm with an impressive ridge over
the Bering and a deep trough over the ALCAN. A warm front was able
to climb over top of the ridge and bring some light snow to the
Pribilofs. It also pushed some of the coldest air back into the
Interior instead of over Southwest AK. Meanwhile, most of
Southcentral experienced its coldest morning of this pattern
this morning as winds died off overnight across most of the area.
Abundant March sunshine is leading to fairly quick warming across
most areas east of the Alaska/Aleutian Ranges.

As the ridge reorients some today and weak energy spills over it,
it will bring the gustier conditions to the westerly gaps such as
Whittier and the Barren Islands. A 145 kt jet moving from the
Seward Peninsula through the Gulf of AK is helping to mix down
some of these gustier winds. A separate 95 kt of the jet
continues to ferry weak areas of lower pressure into the Western
Aleutians. These are bringing some pulses of rain and snow and
small-craft level winds to locations from Atka west.

&&

.MODEL DISCUSSION...
Models remain in excellent agreement which is resulting in high
forecast confidence. The synoptic pattern will change little
through the course of the next several days. Most of the models
have trended slightly stronger with the energy dropping southward
from an Arctic low in the Beaufort Sea on Sun. This looks to
produce another round of strong winds through places like Thompson
Pass and the Copper River Delta. The exact timing and strength of
this remains somewhat in question, but hi-res models were use to
trend winds stronger.

&&

.AVIATION...
PANC...VFR conditions and light northerly winds will persist
through most of the period. Winds should become slightly gustier
around midday Sun as a shortwave passes through the area.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Northwest flow aloft will become more northerly on Sunday with the
passage of an upper level trough. This will increase the offshore
gradient across south central Alaska. Winds could reach warning
levels across Thompson Pass and Valdez, though this event looks
weaker and shorter lived than the event of last Thursday-Friday.
The offshore gradient will weaken again Monday as the main jet
stream pushes westward and the dynamics/upper flow weaken.
Night time temperature forecasts continue to be difficult due to
the large differences between areas that keep the winds all night
and those that de-couple.

&&

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

A front lingering along the Bering coast will provide a slight
chance of snow showers tonight. Building high pressure will
push any lingering clouds to the south. Sunny days and generally
clear and cold nights are then expected through Tue, with some
coastal fog developing late tonight through Sun morning.

&&

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

A front will decay over the eastern bering through Sun with some
lingering snow showers over the Pribilof islands. The eastern
Bering will then dry beneath building high pressure through Tue. A
second front with small craft and gale force wind will bring
rain, mixing with snow at times, to the western and central
Aleutians Sun through Tue before dissipating. A third front will
bring snow and gale force winds to the western Aleutians Mon night
through Tue.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The high amplitude ridge/trough pattern will continue to bring
cold, dry and locally windy conditions to Mainland Alaska through
the week. By Monday night and Tuesday, the upper level ridge axis
will extend from the eastern Aleutians, across the Pribilof Islands
and through the Gulf of Anadyr to well north of 70N. To the east
of the ridge, a very broad upper level trough will extend from the
Arctic Ocean and far Northern Canada, across Mainland and Southeast
Alaska and into Western Canada. The cold air mass currently in
place will continue to be reinforced by the northerly flow aloft
and arctic shortwaves digging down the east side of the upper
level ridge.

The entire pattern will shift gradually east through the week with
the upper level ridge axis tilting east into Southwest Alaska
Wednesday and Thursday and the strongest northerly flow progressing
east across Southcentral Alaska. The upper level ridge will bring
significant warming aloft with it as it pushes onshore bringing
an increasing potential for fog and low stratus to Southwest
Alaska from Wednesday night onward. Throughout the week, frontal
systems will continue to track across the western Aleutians and
into the Bering through the southerly flow on the west side of the
ridge.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch 131.
MARINE...Gale 126 128 185.
		 Storm 127.
 	 	 Heavy Freezing Spray 121 126 127 129-131 138 139 141 185.

&&

SYNOPSIS AND MODEL DISCUSSION...MO
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DS
LONG TERM...JR