Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 PM EST Tue Dec 04 2018

Valid 12Z Sat Dec 08 2018 - 12Z Wed Dec 12 2018

...Guidance Assessment...

The latest model run-to-run consistency and comparability with
respective ensemble means continues to be well below normal
through the medium range period.  Even beginning on day 4, there
is considerable spread and uncertainty.  Because of this, weighed
heavily on the 00Z ECMWF ensemble mean with some 06Z GEFS mean
along with a small portion of the 00Z ECMWF/06Z GFS.


...Pattern Overview and Weather Highlights/Hazards...

The beginning of the medium range period starts with an amplified
upper ridge extending across southeast Alaska into the Interior.
Models are in agreement that this feature will weaken through the
weekend as an amplified trough digs across the coastline of
southeast Alaska, British Columbia and the West Coast. In
addition, there is still spread with the ECMWF/GFS with the
northern stream trough energy in addition to the mid-upper level
trough entering the Bering Sea late in the weekend and into early
next week. The ensemble means continue to be more stable/in better
agreement showing the northern stream trough energy digging across
Alaska later on Saturday and into early Sunday while the closed
upper low approaches the Bering Sea on Sunday.  By Monday, the
upper low sets up in the Bering Sea/western Alaska and will stay
put through midweek. Through the weekend, the southern and
southeast portions of Alaska will have stormy conditions/heavy
precipitation as a deep system moves through the Gulf of Alaska.
By the beginning of next week, another incoming system in the
Bering Sea will approach the Aleutian Islands/western
Alaska--giving way to unsettled/stormy weather. A lingering trough
over southeast Alaska will keep precipitation chances around for
that region through the first half of the week.


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