Small Craft Advisory 364, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
438 PM AKDT Fri May 5 2017

.ANALYSIS AND UPPER LEVELS...
The upper level pattern has shifted from the past few days
bringing the ridge over southcentral Alaska with a large low
moving over the central Aleutians.

The atmosphere over southern Alaska is overall more stable than
the past day or two which is suppressing convection. An
interesting feature to note on visible satellite imagery from
early afternoon is the cloud band that have developed along the
sea breeze boundary over the western Kenai peninsula.

&&

.MODEL DISCUSSION...

The low that is currently near the central Aleutians will have a
triple point low develop along its front as it passes south of
Kodiak Island Saturday. Models are in good agreement with this
development and then having the triple point low rotate back
toward the main low. This is where the models begin to have a
little trouble with the way these lows interact. GFS was
preferred overall with some NAM over southwest mainland Alaska.

&&

.AVIATION...
PANC...VFR conditions will persist. Saturday afternoon may see
winds get a little gusty from the southeast due to the Turnagain
Arm wind.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Expect continued sunny, warm, and dry conditions over much of
Southcentral this evening as a ridge of high pressure moves over
the area. The one exception to this rule will over over the
eastern Copper River Basin and along the Wrangell Mountains which
will see rain showers from a weak upper level trough clipping the
area from the north. This ridge will however quickly depart the
region by Saturday morning as a frontal system moves through the
Gulf, bringing rain and east winds to Kodiak by late tonight, then
spreading into the southern Kenai for Saturday. The good news for
much of Southcentral from this front is that there is increasing
confidence with that downsloping will keep any precipitation
confined to the Gulf Coast/southern Kenai for most of the weekend.
Instead the Anchorage Bowl and MatSu valley's will see increasing
mid-high clouds through Sunday, with gusty gap winds through the
usual areas of Turnagain Arm, as well as along the Knik and Copper
River Valley's.

&&

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

A front approaching Southwest Alaska from the south will move into
the coast tonight. High cloud cover has already spread well
inland, but the main precipitation is still on its way. With
increasing easterly winds, those in the rain shadow of the Alaska
Range, such as King Salmon, Iliamna, and Sparrevohn are unlikely
to see much in the way of precipitation from this as compared with
locations further west. However, those cities will not be spared
from the easterly winds, which will gust to 25-30 mph overnight.
As the front moves inland, it will shear apart as the main energy
associated with it splits between the Bering and the Gulf. The
portion of the energy over the Gulf will help to form a new
triple-point low over the Pacific, which will make its way
northwestward across the Alaska Peninsula and into Bristol Bay on
Sunday, bringing more precipitation and reinvigorating the
easterly winds inland.

&&

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

A sprawling low pressure system centered near the central
Aleutians is bringing gale force winds to the western Aleutians,
with another area over the eastern Bering. As the low weakens and
begins to move east, the gale force winds will also weaken, though
not substantially so until Saturday night. As a new low forms over
the north Pacific and the two merge on Sunday, northerly winds
will become established over nearly all of the Bering. This will
cause gap winds to develop with local funneling between the
islands of the eastern Aleutians, especially Sunday afternoon and
evening.

Occasional snow will continue in Saint Paul this evening until
some drier air now just south of Saint George makes its way in.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Next week will be characterized by high pressure that will build
in over the Bering and try to stretch into mainland Alaska. This
ridging will help push the low over the southwestern Gulf of
Alaska further southward into the North Pacific. However, it will
not be strong enough to fully inhibit afternoon convection for
much of the southern mainland. By the middle of next week, another
low will track eastward over the western portion of the Aleutian
chain, shifting the ridging over the Bering eastward into the
Southwestern coast and mainland by the end of the week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
MARINE...STORM...130 131 GALES...119 120 132 137 138 139 160 175
177 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW
LONG TERM...PEPE