Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
146 PM EDT Fri Jul 13 2018

Valid 12Z Tue Jul 17 2018 - 12Z Sat Jul 21 2018

The model guidance remains in general agreement concerning system
progression across the Bering Sea, northeast Pacific, as well as
northern and western Alaska, but depth issues remain.  In the
northeast Pacific, the 00z Canadian was more southwesterly and
deeper than the other guidance late next week.  The 12z GFS was
stronger with a trough in western AK late next week.  To deal with
these depth issues, a compromise of the 00z Canadian, 00z UKMET,
06z GFS, and 00z ECMWF was used for 500 hPa heights, winds, and
pressures for Monday night through Tuesday night.  Thereafter,
swapped out the UKMET for increasing amounts of the 00z NAEFS mean
and 00z ECMWF ensemble mean to help deal with uncertainty with the
main features.  The remainder of the grids were a 15/15/20/25/25
split of the 06z GFS/12z GFS/00z ECMWF/00z ECMWF ensemble mean/00z
NAEFS mean.

Precipitation chances focus in southeast Alaska early on as a
system in the northeast Pacific moves into Western Canada.  This
was a system the 12z GFS outpaced the remainder of the guidance,
so used a small percentage of it.  Later on, cloudiness increases
statewide with a system crossing the Bering Sea, Aleutians, into
the northeast Pacific.  Rain chances increase on the mainland from
west to east from Wednesday onward.  Shortwaves moving by to the
north should allow intrusions of cool air into the northern
sections of the state, particularly near and north of the North
Slope and within the nearby rugged terrain of the Brooks Range. 

Roth


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