Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
325 PM EDT Mon Apr 09 2018

Valid 12Z Fri Apr 13 2018 - 12Z Tue Apr 17 2018

It appears that most of the forecast spread during the medium
range period will circulate with the Arctic jet. Or more
specifically, whether an amplified upper trough sweeps south and
east through the state this weekend (06z GFS) or enough upper
dynamics separate from the trough to form a closed mid to upper
low, which gradually slips through the state as an upper-level
shear axis (00z ECMWF). The ECMWF has more support from its mean
and somewhat from the GEFS mean, while the GFS remains extremely
consistent with itself. The means appear to align well for the
most part through next Tuesday. All solutions have some sort of
upper ridge building in and attempting to hold, which includes a
formidable surface ridge across the northern part of AK.
Meanwhile, one large upper low starts off over the Gulf of AK/nern
Pacific and sinks south and east, while two powerful cyclones
upstream attempt to knock down the upper ridging and arrive into
the western portion of the state. Overall the ECMWF has more
support than the GFS but by the end of the forecast period, the
GFS gets back into the loop with the consensus and spread is
mostly small. WPC used a 4-way blend of the 00z ECMWF with the 06z
GFS and the two means, 00z EC mean and 06z GEFS mean.

Musher