Small Craft Advisory 317, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
420 AM AKDT Wed Apr 19 2017

.ANALYSIS AND UPPER LEVELS...
Little overall change has happened over Mainland Alaska in the
last 48 hours as the upper level jet dives well south of the
area. This has allowed for broad high pressure to continue to
bring sunny skies to much of the Mainland this morning with light
winds. Over the Eastern Bering, a slowly weakening and dry upper
level trough continues to bring stratus but little in the way of
precipitation to the area. Well west of the AOR the next system
can be seen approaching the Western Aleutians, but with the jet
moving south of the area this low will very slowly move through
the Western Bering over the course of the next 48 hours.

&&

.MODEL DISCUSSION...
Models once again remain in good synoptic agreement in the
current stagnant pattern. Starting Friday there remains good
agreement with a pattern change in the Gulf and the Bering that
will bring more active weather to the area into this weekend.

&&

.AVIATION...
PANC...VFR conditions and light and variable winds will persist
into Thursday.

&&

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

Generally fair skies and mild afternoon temperatures will persist
across the Southcentral Mainland through Thursday. Relatively
weak gap flows are expected through the Matanuska Valley,
Thompson Pass, and the Copper River Delta through tonight.
Thompson Pass and Copper River Basin flows will weaken some
Thursday, but will increase some again Thursday night. Elsewhere,
afternoon and evening sea breezes will be the general rule
through Thursday. With the exception of a few low probability
showers along the Chugach, Talkeetna, and Kenai Mountains much of
Southcentral will remain on the dry side. A front approaching the
southern Gulf Thursday night will increase the easterly flow over
Kodiak Island and bring increased chances of rain or mixed
precipitation types.

&&

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

An upper level low currently centered right along the Kuskokwim
Delta coast will continue to drop south into the far eastern
Bering Sea this afternoon. Satellite imagery already shows that a
bulk of the cloud cover associated with this feature has moved
offshore with just a few clouds lingering from Cape Newenham to
Mekoryuk. Another period of benign and spring-like weather is on
tap for Southwest Alaska through the remainder of the week with
high pressure settling in across the region. Temperatures each of
the upcoming days should be a degree or two warmer than the
previous day which should allow high temperatures to warm into
the upper 40s to mid 50s by end of the week.

&&

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

A weak upper level low will track south across the eastern Bering
Sea through Thursday morning which will bring a few snow showers
to portions of the Alaska Peninsula. Some low stratus has been
observed along the Alaska Peninsula and Pribilof Islands but as
the upper low tracks south, high pressure will quickly fill in
behind and allow for some clearing of clouds today and Thursday.
The central Bering Sea will remain under the influence of high
pressure which will keep skies largely mostly sunny through the
remainder of the week. A frontal boundary associated with a low
pressure system moving into the North Pacific from eastern Russia
will bring gale force winds to the western Aleutians on Thursday.
Another low pressure system will develop along the frontal
boundary and swing toward Shemya late Thursday. Much of the
sensible weather associated with these features will be winds in
the 30 to 35 kt range and periods of light to moderate rainfall.

&&

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

On late Thursday and Friday, mainland AK will be under high
pressure, with a small craft to gale force low near the central
Aleutians. A low will be in the southern Gulf/north Pacific, with
resultant northerly flow keeping much of southcentral AK dry,
except for a few evening showers near mountain ranges.

This weekend into early next week, a series of lows, triple point
lows, and troughs will steadily move along 50 N. This will bring
mainly rain to the Aleutians and the North Gulf coast, with some
afternoon and evening shower activity for inland mountains into
early next week.

The forecast utilizes some gfs and gem through the weekend with
the ensemble solution of WPC next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale 178.

&&

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