Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
340 PM EDT Fri Sep 07 2018

Valid 12Z Tue Sep 11 2018 - 12Z Sat Sep 15 2018

...Guidance/Uncertainty Assessment...

The mid to upper level ridge will remain a dominant feature across
western Alaska through the beginning of the medium range
period--sliding to central Alaska toward the end of the week. A
mid-level closed low is expected to slide northward toward the
western Aleutians by Day 4-5 (Tuesday/Wednesday). This will bring
an occluded system into this region by Day 6/Thursday.  The 12Z
GFS/00Z ECMWF disagree with the handling of this system.  The 00Z
ECMWF, along with the 06Z GEFS/00Z ECENS, shows this mid-level low
moving into the Aleutians, becoming an open wave and being
absorbed into another incoming trough from eastern Siberia.  The
12Z GFS has trended toward this--however, by Saturday, it shows
this mid-level low in the Gulf of Alaska when the 00Z
ECMWF/ECENS/06Z GEFS all have consistently showed a ridge. WPC's
blend was based on the 12Z GFS/00Z ECMWF through day 6, with the
00Z ECMWF/ECENS and the 06Z GEFS used on day 7 and 8.

...Weather Highlights/Hazards...

On Tuesday, mild and dry conditions can be expected across most of
Alaska.  By Wednesday, the chance of precipitation will increase
especially across the Aleutians as the occluded system approaches
the region.  However, the rest of the state will stay dry. 
Western Alaska can expect precipitation chances to increase by
Thursday as the occluded system enters the Bering sea--with the
rest of the state having higher chances by the beginning of the
weekend.  High temperatures will hover around the upper 50s to mid
60s with lows in the 40s/50s.


Reinhart


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