Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
317 PM EDT Fri Jun 29 2018

Valid 12Z Tue Jul 03 2018 - 12Z Sat Jul 07 2018

An upper low and associated trough is forecast to move east
southeast north of Alaska with the models and ensembles getting
into better agreement timing wide than a few days ago.  The
amplitude and track differ, with the GFS still making big run to
run changes. The 12z GFS shunts  a closed 500 mb low south over
central Alaska, 425 miles southwest of its prior run.  The 00z
ECMWF and 00z ECMWF Ensemble mean and 06z GEFS mean cluster better
with the wave amplitude/track, so these solutions were blended,
with the 12z GFS given the least weighting.

The models are trending towards creating height falls in southeast
AK
and coastal waters as the massive anticyclone over the north
Pacific retrogrades west.  Heights and temperatures aloft remain
high across the upper to mid  Aleutians.  The above normal heights
and temperatures favor a pattern of above normal temperatures in
the early to middle portions of next week across southern Alaska,
including in the Aleutians.

A closed low moves north from the north Pacific across the lower
Aleutians into
the western Bering Sea in the middle of next week, possibly
reaching the coast northeast of Kamchatka either Fri or Sat. Minor
timing and intensity differences led to a consensus based approach
to resolve the differences.
The low comes into confluent flow and gradually shears with time,
resulting in low pressure at the surface filling in the Bering Sea.

Manual progs blended the 06z GEFS Mean and 00z ECMWF ensemble mean
with the operational 00z ECMWF. Both the 06 and12z GFS were
subtracted from the forecast days 7-8.

Petersen

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
www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html