Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 251259
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
459 AM AKDT WED MAY 25 2016
.ANALYSIS AND UPPER LEVELS...
Early this morning an upper level ridge is centered over the
Bering with several closed lows around it`s perimeter. The low
across the eastern Gulf of Alaska is moving off to the east with
the stronger system developing along the west side of the ridge.
The low center out west is just south of Shemya acting as a conveyor
belt, advecting abundant moisture northward along the perimeter
of ridge which is currently nudging into the Copper River Valley.
At the surface...a weak front is bringing light rain across the
Kuskokwim Delta. An associated front with the low near Shemya is
moving rain into the central Aleutians with gusty winds along the
boundary across the western Bering.
The current pattern is slowly evolving with multiple low centers
slowed by the building ridge over the Bering. Models are in good
agreement with only minor changes needed using the NAM and GFS.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)..
A broad upper ridge builds east across Southcentral through Thursday
bringing warm temperatures and generally dry conditions. Higher clouds
overshooting the ridge will spread across much of Southcentral today.
Showers are possible along the Alaska Range, Copper River Basin, and
along the Talkeetna Mountains through this evening. on Thursday, the
flow aloft becomes more northerly, so most of the rain/shower potential
will be confined mainly along the Alaska Range and north. A pinch in
the pressure gradient between the building mainland ridge and weak low
pressure trough over the gulf will continue periods of outflow winds
across the Eastern Kenai Peninsula and North Gulf Coast. Gusty
northerly Gap flows are also possible through the Alaska Range
Thursday and Thursday night. Outflow winds will delay the onset
of sea breezes along from the Eastern Kenai Peninsula to the North
Gulf Coast and that combined with downslope warming will allow
afternoon temperatures to climb well into the 60s through
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
One more day of seasonably cool temperatures will be on tap across
Southwest Alaska today as quasi-zonal flow remains entrenched
across the region. Several embedded shortwaves within the upper
level pattern will bring periods of rain to to the Kuskokwim
Valley and Kuskokwim Delta today but will taper off this evening
as a developing North Pacific ridge builds northward across the
southwest mainland. Skies will begin to clear after midnight
tonight and mostly sunny will be seen Thursday morning and likely
linger through the weekend. In addition, temperatures on Thursday
will likely be 10 to 15 degrees warmer than those observed today
with high temperatures in the mid 60s across the region. These
warm temperatures will also persist through the weekend and look
to be a couple degrees warmer each day heading into the weekend.
Offshore flow will develop on Thursday which will aid in keeping
Southwest Alaska dry and help continue the mostly sunny period.
Should be a beautiful Memorial Day weekend across Southwest
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
An occluded front continues to push across the western half of the
Bering Sea this morning with scatterometer data showing gale
force winds just west of Adak. This front will continue to push
slowly eastward through this evening before it begins clashing with
a building North Pacific ridge building across the eastern Bering
Sea. Gale force winds will be seen across the Central Aleutians
through this evening before it should weaken below gale force
winds as the front continues to weaken. The front looks to stall
just to the west of the Pribilof Islands which will keep the
Pribilofs in a nice period of weather through weekend although fog
looks possible (as is typical with high pressure over the Bering
Sea). Showers will continue across the western half of the Bering
Sea as the low near Shemya meanders northward. By Friday morning
a few showers could be seen across the Eastern Aleutians and southern
tip of the Alaska Peninsula as a weak area of low pressure over
the North Pacific fizzles out.
.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...Gales 175 176 177.
SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC