Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 PM EDT Wed Aug 08 2018

Valid 12Z Sun Aug 12 2018 - 12Z Thu Aug 16 2018

The guidance showed reasonable agreement early on with a cyclone
moving in from the southwest which contains some of Shanshan's
remains. Bigger issues involve the cyclone trailing it, of which
the 12z GFS and 00z Canadian show a stronger reflection.  To
account for the uncertainty, used a combination of the 00z
Canadian, 06z GFS, 00z UKMET, and 00z ECMWF early on.  Start
transitioning mid period/Monday to using more 00z NAEFS and 00z
ECMWF ensemble mean solutions to help account for uncertainty. 
This led to excellent agreement with the 500 hPa height preference
from yesterday, though it led to a deeper/stronger cyclone
impacting Alaska early on and faster moving cold fronts through
the northeast Pacific ocean.  The remainder of the grids
(temperature, dew point, clouds, precipitation chances, and
weather) were based on an even blend of the above deterministic
and ensemble mean guidance.

With the anticipated deep layer cyclone over the state through the
period, this promises to be a cloudy and unsettled time
weather-wise for Alaska.  Heavy rains spread from south to north
through the state from Saturday night into Monday night before
focusing in the AK peninsula Monday night through Tuesday.  The
heaviest amounts near the coast could reach 5" a day locally,
particularly in south-central AK, with amounts in southeast AK
more uncertain, though likely to be heavy.  Light to moderate rain
is expected Wednesday onward to the north of a cyclone attempting
to move towards the state from the south.  The latter system's
depth and location remains unclear, so exact impacts remain
uncertain.

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