Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
342 PM EDT Sat Jun 30 2018

Valid 12Z Wed Jul 04 2018 - 12Z Sun Jul 08 2018

...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...

Models and ensembles identify three main medium range time period
weather systems to effect Alaska and adjoining waters. This
includes a closed trough/low to drift westward over the western
Bering Sea mid-later next week as mainly a maritime interest, a
southern arctic trough/low ready to dig over the eastern interior
then Gulf of AK next week, and the approach toward the Aleutians
of the extratropical low associated with current West-Pacific
system Prapiroon in about a week. WPC progs show a threat of a
decently deep low there given the former tropical history.

Overall, the WPC product suite was primarily derived from a blend
of the ECMWF and GEFS/ECMWF ensemble means day4/July 4th, but
relied primarily upon the ensemble means days 5-8 amid growing
forecast spread that is mainly associated with the evolution of
arctic troughing into the interior and Gulf of AK. The 00 UTC
ECMWF/ECMWF ensembles dig much more ample height falls across the
region than recent GFS/GEFS ensembles. The 12 UTC ECMWF has backed
off from the 00 UTC ECMWF, but the latest version still seems in
line with a blend of GEFS/ECMWF ensemble means. This feature
offers potential amplitude to support/spread some enhanced
precipitation through the North Slope over the holiday, the
eastern interior Thu/Fri, then the eastern Gulf of AK next weekend.

Schichtel

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