Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 250000
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
400 PM AKDT TUE MAY 24 2016
.ANALYSIS AND UPPER LEVELS...
An upper level wave is currently bringing showers and cloud cover
to the Copper River Basin as it traverses eastward. To the west, a
broad ridge encompasses much of the Bering and is supporting an
extensive stratus deck with patchy fog. Broad westerly flow has
helped to push moisture and associated stratus inland across the
Kuskokwim Delta and western Bristol Bay, resulting in cool and
cloudy conditions. Meanwhile, skies have remained clear across
south-central and eastern portions of the western mainland. In
the western Bering, the weather pattern is much more active with a
gale strength low approaching Shemya.
Models remain in fairly good agreement on the shortwave over the
Copper River Basin progressing eastward today. There are more
differences in the timing and intensity of the new low entering
the western Aleutians. The NAM indicates a slightly weaker
associated low level jet and indicates less precipitation than the
other models with this system and is the outlier. As a result...a
blend of the GFS and ECMWF was favored...especially for the west
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)..
A shortwave trough is currently moving through the Copper Basin,
bringing rain and showers to that area. Behind the low, offshore
westerly winds are continuing to blow through favored gaps, and
will continue through the night and increase across northern
Prince William Sound, as well. On Wednesday, a ridge of high
pressure will begin to build over the eastern Bering and southwest
Alaska, but this will also bring increasing mid-level and high-
level clouds. Some of this moisture will be wrung out across the
Alaska Range and Talkeetna Mountains tomorrow, but any activity
will be rather light and sparse. On Thursday, the ridge builds
farther east, putting Southcentral into a favorable northwest flow
aloft along with an offshore pressure gradient. This will allow
for the beginning of an extended dry and warm period that will
likely continue through the Memorial weekend.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A seasonably cool and cloudy pattern will linger into wednesday
night as quasi-zonal flow remains entrenched over the area on the
northern periphery of a developing North Pacific ridge, with a few
weak embedded disturbances bringing periods of rain to the
Kuskokwim Delta and Valley. Thursday will bring a dramatic shift
to a much warmer and drier pattern as the stout ridge builds over
the southwest mainland and evolves into a closed upper high. This
will yield high temperatures on Thursday running upwards of 10
degrees (F) above Wednesday`s highs, with skies rapidly clearing
as dry offshore flow develops.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A gale force front associated with the Northwest Pacific low
nearing the Western Aleutians will move to the central part of the
chain late tonight into Wednesday and gradually weaken in place
through Thursday as it encounters the stout ridge building to the
east. This will yield rain and gusty south winds, transitioning
to more of a showery regime by Thursday across the western half
of the Bering. Meanwhile, the Eastern Bering will see benign
conditions characterized by areas of fog beneath the building
.LONG TERM FORECAST (Days 3 through 7)...
The big story will be the upper level amplified closed high
pressure building into Southwest/Southcentral Alaska regions for
this upcoming weekend. This will bring plenty of beautiful sunny
skies for the aforementioned regions accompanied by warmer
temperatures, and drier conditions. Look for temperatures to
reach in the upper 60s to lower 70s for the Southwest Alaska
region. While, the Southcentral Alaska region will have
temperatures in the mid 60s to mid 70s. Look for the warmest
temperatures to occur in the Matanuska and Susitna Valleys, and
the Copper River Basin. Also you will have the normal sea breezes
throughout this weekend.
As this the high pressure builds into the southwest region there
will be marine layer stratus/fog through the Central/Northern
Bering Sea during the latter part of this week. By Thursday the
Western Aleutians will have a 994 mb gale force low, and tracks
towards the Kamchatka Peninsula by Friday before dissipating. This
will bring a showery weather regime as the system exits the
region. Then by Saturday, another low pressure system enters the
Western Aleutians, and becomes elongated extending into the
Central Aleutians. While the Eastern Aleutians will a have a North
Pacific Low tracking just south of Cold Bay by late Friday
evening. This system will track westward along the chain before
phasing in with the low pressure system over the Western Aleutians
on Saturday. This will bring a swath of moisture accompanied by
gale force southeasterly flow into the Central Bering Sea heading
into Monday. Overall the forecast confidence remains above average
with the different synoptic features as we head into the weekend.
MARINE...Gale Warning 175 176 177 178.
SYNOPSIS AND MODEL DISCUSSION...en
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...cb