Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
409 PM EDT Fri Jul 27 2018

Valid 12Z Tue Jul 31 2018 - 12Z Sat Aug 04 2018

A major pattern change appears to be in the making as an upper low
initially over the Bering Sea will be replaced by a deep layer
ridge building in from the south toward the Aleutians during the
latter half of next week.  The deterministic models still show a
wide variety of solutions on handling the energy of the weakening
cyclone as it heads toward the west coast of Alaska next
Wednesday.  It appears the remnant energy will split into two
pieces--one turns northward into the Arctic Ocean while another
dips down across mainland Alaska later next week and into the Gulf
of Alaska next weekend.  The ensembles are in general agreement on
this scenario as a deep layer closed anticyclone forms south of
the Aleutians during the latter half of next week.  The GEFS has
been the strongest and further west on building the closed
anticyclone.  The 12Z GFS has backed off on the strength of this
anticyclone and it agrees pretty well with the 00Z EC mean which
indicated less ridging.  It appears that the 00Z EC mean offers
the best starting point for this volatile pattern and the WPC
package trends toward mostly the 00Z EC mean solution in
combination with the 00Z ECMWF and the 12Z GFS.  The extratropical
transition of a western Pacific tropical cyclone should support
less ridging over the Aleutians, and the 12Z ECMWF trends toward
less ridging as well.


Kong


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