Small Craft Advisory 379, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
509 PM AKDT Wed May 10 2017

.ANALYSIS AND UPPER LEVELS...
The upper level ridge is firmly over southwest mainland Alaska
today with the remnants of the upper level trough extending over
the Alcan border. This is keeping the area of instability
relegated to the Copper River Basin again today. The convection
from yesterday in the Copper River Basin collapsed into a stable
stratus layer in the lower elevations causing a cool and cloudy
day which will inhibit convective development in the middle of
the basin. Farther northwest it remains quite unstable and
elevated heating along the mountains will trigger more showers
and possibly a thunderstorm again this afternoon/evening. Southwest
mainland Alaska is stable under the ridging with a large area of
clear skies over Bristol Bay into the eastern Bering Sea. The next
low is currently near Amchitka and will continue its slow east to
northeastward trajectory the next few days.

&&

.MODEL DISCUSSION...
Models are once again in quite good synoptic agreement. The only
notable issue is the farther northwest solution the GEM is
showing for the central Bering Sea low this weekend. The other
three models have a tight cluster for the low center and have
remained consistent for a number of runs.

&&

.AVIATION...
PANC...VFR conditions persist. Winds should remain relatively
light with afternoon and evening sea breezes.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A ridge axis extending from a dome of high pressure over the
North Pacific will result in a drying trend. So far today in west
Anchorage, the high temperature has reached 60F, which is the
first time for 2017. The models hold on to convective parameters
over Susitna Valley and The Copper River Basin through the weeks
end. As time elapses, the pressure gradient will increase on the
northern edge over Shelikof Strait kicking up winds and waves. A
new front will push into the region bringing precipitation to
Kodiak later in the forecast period.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The southwest mainland will remain in a very benign pattern for
the next few days as the upper level ridge slowly weakens over
the west coast. Thursday looks to be the warmest day of the week
beneath mostly sunny skies, with a very dry air mass and the
absence of any forcing mechanisms helping to mitigate any
diurnally driven convective activity. A weak Bering Sea front
will bring a chance of rain to the coast starting Thursday night,
with slightly cooler and cloudier conditions spreading inland by
Friday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A gale force front will rapidly push north and east across the
Bering tonight and Thursday as its parent low makes slow eastward
progress across the Western Aleutians. This will bring a quick
shot of rain to the Aleutians and Akpen over the next 24 hours,
with conditions generally improving by Friday as the low diminishes
in intensity over the central Bering and the front pushes inland
over southwest Alaska.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Beginning the extended period forecast Friday evening, a closed
low will be in the process of moving from the Eastern Bering Sea
into Southwest Alaska. The numerical models have not handled this
system well the past three days, but there is now high confidence
in a track from Southwest Alaska into the North Gulf by Saturday
night. This low will be occluded, so there will not be much of a
moisture tap associated with it, but it will spread light rain
into all of Southwest Saturday before moving east. While the low
will be digging into the Gulf Saturday night into Sunday, enough
cyclonic flow aloft (DCVA) will help support organized rain/showers
across Southcentral before the low moves south by Monday morning.
Thereafter, weak upper flow over Southern Alaska will bring drying
conditions although afternoon diurnal showers will remain a threat.

Farther west, a broad and slow moving upper low will form southwest
of Shemya Friday night with the associated front moving north
toward the Aleutian Chain. This front will slowly move east
through Tuesday, bringing widespread light rain to that area
before lifting north toward Southern Alaska Tuesday and Wednesday.
This front looks rather weak, at this juncture, and will not have
much upper support with it, but this will increase clouds and
precipitation chances to Southern Alaska after a brief dry period
Monday. The front falls apart Thursday, leaving shower activity
and cloudiness across the southern mainland.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 170 173 174 175 176 177 179 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...PZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...JA