Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
341 PM EDT Thu Jun 07 2018

Valid 12Z Mon Jun 11 2018 - 12Z Fri Jun 15 2018

The Alaskan medium range forecast has become uncertain over the
past two days over higher latitudes. This has been due to a change
in ensembles and models regarding a closed arctic mid-upper level
trough/low and potential digging of potent shortwave energy/height
falls southward into the mainland. Was reluctant to make too
radical of a change to WPC continuity, but a stronger upper high
over northeast Russia tends to support some deeper flow into
Alaska. Opted earlier to blend guidance to show some trend in the
surface fronts/pressures and 500mb progs without jumping whole hog
to the amplified 12 UTC GFS. The 12 UTC ECMWF has since trended
more toward amplitude, so the WPC sensible weather grids were
aligned a bit more in that direction.

Underneath, model/ensembles remain much better clustered with a
series of deepened lows and a composite blend of the guidance
seems reasonable. This takes a lead system eastward over the
eastern Pacific before lifting northeastward midweek into the
southern Gulf of AK in a weakening state. This should be followed
by an upstream system tracking to the south of the Aleutians that
seems slated to turn northeastward toward the AK peninsula in
about a week. Ensembles suggest building ridging along 140W near
50N by next Thursday, which could inhibit more of an eastward
track of this system. These lows mainly present a maritime threat
including high winds/seas/rains.

Schichtel

WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can be found at:

http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html