Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
420 PM akdt Thursday Jul 2 2015
Analysis and upper levels...
stacked middle to upper-level closed low continues to move away from
the area from the Yukon toward the northwest territories this
afternoon. Meanwhile...the expansive area of stratiform rain
coinciding with a robust 700-mb jet streak from the interior south
through the northern and western Susitna Valley continues to
disintegrate as a middle-level shortwave ridge builds across the
Alaska Range. In the upper levels...a northwest-southeast trough
axis is situated along a McGrath to Seward line...and represents
the edge of drier air in the middle-levels of the atmosphere.
To the west...another upper low resides over the western
Mainland. This trough will move very slowly through the western
interior just to the north of the aor over the next few days.
Persistent ridging that has existed over the eastern Bering
continues to hold even as an Aleutian low continues to spin near
Adak. This ridge is expected to hold through the work week...while
the Aleutian low will remain nearly stationary over the central
models are in good agreement synoptically. The upper level trough
axis over the upper Cook Inlet region will continue to move north
and east through the Copper River basin overnight...and will help
to clear out the moisture-rich lower levels of the atmosphere from
this afternoon and evening. Conditions become a bit more unstable
Friday with southwest flow developing aloft for Saturday...but
with the better lift and moisture confined to inland areas with an
upper level ridge along the coast.
A front pushing north along the east and northeast side of the
anchor low near the central Aleutians will push a front toward
southern Alaska. This front will lose its significant upper level
support and start to shear apart Saturday...but will still bring
rain and wind to coastal locations and some showers inland. Gusty
winds should mainly be confined to Portage Valley and Turnagain
Arm Friday into Saturday...as well as through gaps in the
Aleutian Range over southwest Alaska.
Southerly flow will keep cloudy and moist low- to middle-level
conditions in the area with a chance of rain showers...mainly
inland Friday and toward the coast Saturday. With the low- to middle-
level moisture will be very limited instability...with just a
slight chance of a thunderstorm over the Susitna Valley and Copper
River basin toward the Alaska Range Friday. Under transitory
ridging Friday southwest Alaska will be able to dry out...with
skies becoming sunny and clear especially toward the Kuskokwim
Delta. Humidity values may drop into 25 to 30 percent range in
the afternoon and evening hours...with humidity values in the 30s
over the remainder of southwest Alaska.
Saturday will see a solid overcast across the region with a front
moving inland...with rain toward southwest and showers inland over
southcentral. Gusty winds through southeast-northwest oriented
terrain gaps will increase beginning Friday...but with plentiful
moisture aloft humidity values will stay well above critical fire
Short term forecast southcentral Alaska (days 1 and 2)...
Showers associated with the low moving into Southeast Alaska will
gradually diminish tonight. Some clearing on Friday will allow for
enough afternoon heating over mountains to trigger a few
showers...and over the Alaska Range and talkeetnas isolated
thunderstorms are possible. Friday night into Saturday clouds
associated with a front from the Gulf will spread over the region.
This will bring rain to coastal areas...with areas on the Lee
side of coastal mountains only receiving some showers.
Short term forecast southwest Alaska (days 1 and 2)...
a weak trough dropping into the Mainland from the northwest keeps
isolated to scattered showers over the Kuskokwim valley...barely
clipping interior portions of Bristol Bay. This trough will battle
with a ridge to the south over the next couple days...keeping any
chance for showers over the northern Kuskokwim valley while a
warmer air mass begins to push in from the south. Friday will
bring a quick spike in afternoon temperatures before a front
pushes northward from the Pacific on Saturday...moderating
temperatures and spreading rain over much of the Mainland through
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
easterly flow is beginning to pick up ahead of a front currently
arcing from the eastern Aleutians around a low pressure system
over the central Aleutians. The front will not make much progress
until a different disturbance picks it up and moves it northward
Synopsis and model discussion...cirrocumulus
southwest Alaska/Bering Sea/Aleutians...ml