Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EDT Thu Jun 14 2018

Valid 12Z Mon Jun 18 2018 - 12Z Fri Jun 22 2018

...Heavy rainfall for Southwest/Southern Alaskan and Panhandle up
into the interior...

...Guidance Assessment and Weather Highlights...

Models and ensembles agree with synoptic scale depiction of an
anomalously amplified flow pattern over Alaska and vicinity for
the next week. This lingering pattern is highlighted aloft by a
moisture/precipitation laden closed mean trough anchoring over the
southeastern Bering Sea and potent ridging spread from western
Canada to the eastern Alaskan interior. A series of low pressure
systems are slated to lift poleward on the western peripherty of
the ridge, with a lead system including the moist extratropical
remains of former western Pacific tropical storm Maliksi. While
the smaller scale specifics of this low train and flow
interactions remain quite unclear, it is very likely that deep
layered moisture feeding inland into southwest and
southern/southestern Alaska downstream will fuel widespread and
terrain enhanced heavy precipitation onshore, with lessening but
locally enhanced activity working into the west-central interior.
Mid-upper level arctic mean troughing prominent overtop to the
north of the state offers less predictability, but guidance
overall shows the feature and cooling/unsettling effects through
northern Alaska weakens and ejects into midweek.

The WPC Alaskan product suite was mainly derived from a composite
blend of the 12 UTC GFS/GEFS mean and 00 UTC ECMWF/ECMWF ensemble
mean. Applied higher weighting to the deterministic models days
4/5 (Monday/Tuesday) and transitioned emphasis Wednesday onward
toward the ensemble means amid growing forecast spread.  

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