Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
413 PM EDT Tue Aug 06 2019
Valid 12Z Sat Aug 10 2019 - 12Z Wed Aug 14 2019
An amplified flow pattern will be characterized by an upper low in
the Bering Sea and to the northeast of Alaska with stretched
ridging across the Bering Strait into western Alaska.
Models/ensemble were in decent agreement overall but varied in the
handling of each feature (including exiting troughing initially
near the Panhandle--though a blend of the 12Z GFS and 00Z
ECMWF/Canadian offered a good basis there).
To the north, question is how the strong upper low initially near
the North Pole translates southeastward toward Banks Island in the
Canadian archipelago; specifically, in one piece/bodily (GFS and
maybe the UKMET) or in a lead and then following piece
(ECMWF/Canadian). Though the ensembles may mute the evolution,
they seem to lie more in the camp of the ECMWF/Canadian that sends
one vort max Sun/Mon before the second piece shifts the low center
farther southeastward.
In the Bering Sea, a multi-model/ensemble consensus served fairly
well as spread increased only modestly by next Tue but then
exponentially by next Wed. Opted to discount any model that
brought in a strong cyclone ahead of the ensemble mean consensus
which eliminated the GFS/Canadian there. The 00Z ECMWF was
acceptable despite its shifts away from the means this weekend as
it was still within ensemble tolerance.
This pattern favors widespread rain over the Aleutians ahead of
the slow-moving front in the Bering Sea over the course of several
days. Scattered rain/convection is likely over portions of the
interior ahead of the baroclinic zone that will set up on the
height gradient south of the Brooks Range. Temperatures will be
below average over much of northern/northeaster areas on NW flow
aloft, but above average over southwestern Alaska under upper
ridging.
Fracasso
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
No significant hazards are expected over Alaska during this
forecast period.
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