Small Craft Advisory 316, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...DELAYED
National Weather Service Anchorage AK
511 PM AKDT Tue Apr 18 2017

.ANALYSIS AND UPPER LEVELS...
Upper level high pressure is causing clear skies over most of
mainland alaska as well as the Gulf of Alaska. An upper level low
in the eastern Bering sea is keeping some clouds over the
Kuskokwim Delta today but these should decrease overnight as the
low moves westward.

At the surface the high pressure is centered over the Arctic Ocean
just north of the state. Low pressure well south of the Gulf of
Alaska is keeping the pressure gradient from being too tight over
the area which is keeping the strongest winds in the Thompson Pass
area at around 25 to 30 mph.

&&

.MODEL DISCUSSION...
Models remain in good synoptic-scale agreement the next few days.
Late in the week there are some timing and low track issues with
the systems approaching the Bering Sea and Gulf of Alaska.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

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

The trough along the north Gulf coast has largely dissipated now,
as evidenced by a lack of cloud cover or strong winds. So without
any synoptic features driving the large-scale weather, a
continuation of nearly universal clear skies due to a dry
atmosphere from top to bottom remains the forecast. The only
weather concerns will be the gap winds that develop in the
morning hours, falling relative humidities, and the potential for
sea breeze development in the afternoon.

Gap winds will continue to develop in the Matanuska Valley and
Copper River Delta for the next couple mornings as high pressure
inland pushes cool air through the gaps. Relative humidities will
continue to fall as progressively drier air mixes in. While it is
April and temperatures are warming on land, it is not quite warm
enough yet for strong sea breezes to be expected. However, Weak
sea breezes are expected in Kachemak Bay and Resurrection Bay for
the next few afternoons. For Valdez, drainage winds should
continue to keep the sea breeze from reaching the shore for now.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Clear condition inland with more cloud cover and a chance of rain
near the coast for the next couple days. An upper level low
pressure spinning off the coast will be the main driver of
mainland weather through Thursday. It will mainly stay offshore
with the most expansive cloud cover along the coast. Any chance of
precipitation will remain along the Kuskokwim Delta coast and the
western Bristol Bay area, also along the coast. Interior Bristol
Bay, and the Kuskokwim Valley should remain clear. Generally light
offshore northerly winds will remain for most areas. Temperatures
will be warmest inland with highs in the 40s for clear areas and
highs in the 30s for cloudy areas.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Light to moderate northerly flow with snow showers for the central
and eastern Bering Sea. These conditions will hold through
Wednesday when the flow will weaken and showers will taper off.
The western Bering will stay under a southeasterly flow regime as
a front approaches from the northwest Pacific. The front will
strengthen to gale force as it approaches with rain barely
reaching the western chain.

&&

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

On day 3 (Thu night through Fri) 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.

For days 4 through 7 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...None.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...DS