Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
521 am akst Monday Feb 8 2016
Analysis and upper levels...
The region remains under the influence of a powerful North
Pacific jet stream...which continues to develop strong lows in the
North Pacific before they move into the Gulf of Alaska. Across
the north central Pacific south of the Aleutian chain...there is a
mature hurricane force low. Farther east...there is a secondary southerly
upper jet and associated moisture stream moving into the Alaska
Panhandle. Over southern Alaska...the main weather feature of
interest is the leftover remnants of a once low end storm force
(winds 50 to 60 knots) low and front...which is currently tracking
over the Alaska Peninsula. East of this low...showers are
impacting the northern Gulf Coast and Kenai Peninsula...with
enough cold air to support snow and mixed rain. Across southwest
Alaska...the combination of downslope flow and a northeast surface
pressure gradient is keeping most inland locations dry with only
showery conditions this morning.
The models are in excellent agreement through the short term
period...and they are in very good agreement with the large scale
synoptic pattern as far out as the next week. Forecast confidence
is very high.
Short term forecast southcentral Alaska (days 1 and 2)...
with ridging sitting off to the east...southerly flow will
continue to impact the southcentral for the next couple days.
Several lows will move through this flow from the south with the
first currently bringing rain and snow to the north Gulf Coast.
The second will move towards the Gulf Tuesday night with its front
hitting the coast also overnight Tuesday. The front will bring
another round of precipitation and warm air from the south. The
majority of the precipitation will stay on the Gulf side of the
Short term forecast southwest Alaska (days 1 and 2...Monday and
tue)...the pattern remains mostly unchanged. Yet another low is
preparing to cross the Alaska Peninsula today. As it does so...it
will cause cool northeasterly flow to give way to warmer and
moister southeasterly flow. This should result in some gusty
conditions...especially through favored gaps...and warmer
temperatures by this afternoon. As the low moves northwest
paralleling the coastline...precipitation will overspread the
western half of Bristol Bay. Areas in the Lee of the mountains
will initially stay slightly drier under cross-barrier flow. The
best chance for precipitation will be along the Alaska Peninsula
into the western convective available potential energy. It will likely start as a rain/snow mix
before changing over to all rain.
As the low tracks toward the Bering Strait on Tuesday...it will also
cause winds to switch around across the yk Delta. It will bring a
chance for a passing rain and/or snow shower...mainly to coastal
areas. A shortwave ridge will move over the area late Tuesday bringing
drier conditions and a brief reprieve to the gustier winds.
Short term forecast Bering Sea/Aleutians (days 1 and 2...Monday and
tue)...a storm-force low continues to track along 385 nautical
miles south of the Aleutian chain. But for the chain itself
though...only some gale-force easterly winds and light
precipitation will make it into the area. The low will drift
slowly east through the day as it weakens. By early Tuesday...it will
push the warm occlusion into Dutch Harbor bringing rain and a
chance to southeasterly winds. This low will then dominate the
rest of the period with the warm occlusion slowly stretching back
toward Atka and Adak with colder northeasterly flow and snow
showers impacting the western Aleutians.
Long term forecast (days 3 through 7)...
the long term forecast remains predominantly dry across the
southern Mainland with storms systems continuing to bring active
weather across the southern Bering and Gulf of Alaska. Tuesday
night into Wednesday a low developing across the eastern Pacific
moves a front into the southern Gulf on its track toward the
Alaska Peninsula. Gusty gale winds and rain will spread east to
west across the Gulf with stronger winds possible if a deeper
surface low develops. Gusty winds along channeled coastal terrain
is expected to increase early Wednesday as this next system
tightens the pressure gradient along the northern Gulf. Models
are struggling with how to handle the low as it nears the Alaska
Peninsula Wednesday night as a second closed low in the North
Pacific picks up a faster easterly track on the south side of the
Aleutian chain. Due to this uncertainty in the Middle Range forecast
changes are likely to be made for winds and precipitation across
the western Gulf and the eastern Bering.
Marine...gale 130 131 132 136 155 172 174 176 177 351 352
Synopsis and model discussion...ja
southwest Alaska/Bering Sea/Aleutians...MO