Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
710 PM EDT Sun Aug 22 2021
Valid 12Z Thu Aug 26 2021 - 12Z Mon Aug 30 2021
...An Active Weather Regime for Alaska..
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of reasonably well clustered solutions from
the 12 UTC GFS/ECMWF/UKMET/Canadian days 4/5 (Thu-Fri). This
solution is also supported by the National Blend of Models and
GEFS/NAEFS/ECMWF ensemble means whose guidance seems more run to
run stable into the days 6-8 period amid growing model forecast
spread. This Alaskan WFO collaborated forecast strategy maintains
good WPC continuity.
...Pattern Overview and Weather/Threats Highlights...
An amplified flow pattern next week should maintain wet and
unsettled conditions across much of Alaska.
Upper energies interacting with an Arctic frontal boundary will
support organized precipitation across northern and Interior
Alaska. In particular, an organized low pressure system reaching
northwest/western Alaska Thursday will bring increased chances for
enhanced precipitation into the region and inland across the North
Slope/Brooks Range and the Interior Thursday into Friday.
Additionally, Arctic Ocean system development also favors
organized precipitation underneath into the North Slope next
weekend. This pattern supports below normal maximum temperatures
down across much of Alaska.
Meanwhile to the south, onshore fetch ahead of a series of
energetic systems set to work across the Gulf of Alaska this week
will direct significant moisture to fuel moderate to heavy
rainfall from the southern coast to the Panhandle. Higher
elevations will also see measurable snowfall. An exiting lead
system over the eastern Gulf into Thu will give way to a more
complex and amplified system to track from just south of the
Aleutians and AKpen Thu into Fri that is expected to solidify
across the northern Gulf later week into next weekend.
Upstream, there is more uncertainty with system development and
progression into days 7/8 from the west Pacific/East Asia of a
deepened storm system to approach the western Aleutians/Bering Sea
that may offer enhanced rainfall potential given some
extratropical connection to current tropical system OMAIS.
Schichtel
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html