Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
206 PM EST Tue Nov 13 2018

Valid 12Z Sat Nov 17 2018 - 12Z Wed Nov 21 2018

Models and ensembles continue to agree on the overall synoptic
scale features of the medium range forecast but differ in the
details especially towards the second half of the forecast. Early
in the period (Saturday and Sunday), both the 12Z GFS and 00Z
ECMWF agree with a ridge dominating the eastern half of Alaska
with a closed upper level low in the Bering Sea.  At the surface,
an occluded system will move across the Aleutians and by the end
of the weekend enter into the Gulf of Alaska. The 12Z GFS and 00Z
ECMWF are in line with each other in terms of timing of these
features--with the 00Z ECMWF being slightly slower and more
aggressive with the upper low. By early next week, the upper low
is expected to slide eastward over Southwest Alaska while the
ridge across the Alaska Panhandle weakens. By Wednesday, A trough
will dig across the Gulf of Alaska, stretching southward toward
the West Coast, with ridging across the Aleutians and the Bering
Sea. However, another upper low, bringing a strong surface low,
will start to approach the western portions of the Aleutians.
During the Mon - Wed time frame, the operational 00Z ECMWF/12Z GFS
begin to have detailing issues.  However, the 00Z ECMWF ensemble
mean and 06Z GEFS mean overall agreed well--thus during this time
frame, increased the use of the means.

With multiple systems moving across the Aleutians and the Gulf of
Alaska, the Aleutian islands eastward into the Alaska Panhandle
can expect a wet pattern. The Alaska Panhandle particularly can
possibly expect heavy precipitation through the weekend and into
early next week.  After Saturday, Southwest Alaska will have a
decrease in the chance of precipitation and will stay quiet
through midweek. 


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