Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
710 PM EDT Sun Jun 27 2021
Valid 12Z Thu Jul 01 2021 - 12Z Mon Jul 05 2021
...Unsettled weather expected from portions of the Aleutians to
the South-Central Coast...
...Overview and Guidance/Predictability Evaluation...
The latest models and ensembles continue to advertise a large deep
cyclone will wobble between the Aleutians and the Bering Sea.
Eastward progress should be halted by an upper level ridge axis
over eastern mainland Alaska and western Canada. There's a bit of
dispersion amongst the guidance concerning shortwaves moving
around the southeast and east side of the cyclone towards
southeast AK and western Canada, with the 12z GFS strongest and
the most northerly and other guidance more southerly. The
ensemble means showed dispersion as well, with the 00z NAEFS mean
extremely elongated and weak, implying a great deal of spread in
its Canadian and NCEP ensemble members, making it less useful.
The 12z GEFS mean followed its operation solution. The apex of
the ridge in the Arctic Ocean argues for a solution south of the
12z GFS with the shortwave, more in line with the 12z ECMWF. From
Thursday into Saturday, a compromise of the 12z GFS and 12z ECMWF
was reasonable. Thereafter, used a compromise of the 12z ECMWF
and its ensemble mean. Compared to continuity, this slowed
frontal progression to the east and delayed/lowered rain chances
for the AK Panhandle, which was coordinated with the AJK/Juneau
forecast office.
...Weather/Threats Highlights...
The Aleutians into the AK Peninsula and Kodiak Island are expected
to produce periods of showers and gusty winds, with some heavy
rainfall. As upper level ridging remains fairly persistent across
eastern AK, east-central AK should be warmest with highs in the
70s and 80s, with slightly cooler conditions for the Panhandle.
South-Central Alaska and back to the Aleutians should remain near
or below normal temperature wise underneath mostly cloudy skies.
Roth
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards 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