Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Thu Aug 02 2018

Valid 12Z Mon Aug 06 2018 - 12Z Fri Aug 10 2018

The upper ridge will begin to flatten by Monday over the Aleutians
which will drive the first system that will impact the Aleutians
on Monday and western Alaska by Tuesday. By this time, the 00Z
ECMWF and 12Z GFS were slightly different with this system--with
the GFS being faster, farther north and stronger with the surface
low.  However, these differences are evened out by Wednesday as
the surface low slowly moves eastward along the northwestern
Alaska coast. High pressure builds across the Aleutians and
western Alaska ahead of the next incoming system.  A system in the
western Pacific is forecast to loop around high pressure centered
across the eastern Pacific and move toward Alaska as an
extratropical system by Friday.  The GFS has consistently been
strong with this surface low and has trended toward this system to
move slower/farther north. The 12Z CMC also aligns with the GFS.
The ECMWF has not been consistent with the placement nor the
strength of this system--with the 12Z ECMWF showing it to be much
flatter.  The 00Z ECENS lines up with the 00Z GEFS/CMC
mean--albeit weaker. WPC used a blend of the 12Z GFS/00Z ECMWF and
increased the usage 00Z ECENS/NAEFS by day 6/Wednesday through the
rest of the period.

Overall, the pattern is still expected to be wet for the
panhandle. The first round of precipitation will move across
Alaska on Monday.  By Tuesday, a frontal system will sweep across
the Aleutians and deliver moderate to heavy precipitation along
this area in addition to the Alaska Panhandle and southeast
Alaska.  Rainfall chances will begin to increase as the potential
deepening system approaches the Aleutians on Friday. Temperatures
are expected to be seasonably mild through the period.


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