Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
332 PM EDT Fri May 18 2018

Valid 12Z Tue May 22 2018 - 12Z Sat May 26 2018

Models and ensembles remain in good agreement on the longwave
pattern that features a slowly dissipating upper low in the Gulf
with another moving through the Bering and along the Aleutians.
Upper ridging in western Canada will be slow to move back westward
into eastern Alaska and the Panhandle, probably after the medium
range period. This will result in several days of SW flow into SE
Alaska with scattered showers and cool temperatures, extending
northward into the Interior north of the Alaska Range.

Models start to diverge in the handling of the Bering system
around next Thursday as well as with the formation of an upper low
south of Haida Gwaii. The 12Z GFS and 00Z Canadian were closer to
the ensemble consensus with the upper low south of 45N, but the
00Z ECMWF was also close to the consensus with the Bering system,
so a blended solution was utilized which maintained continuity
well. As the upper ridge attempts to build over western Canada,
the lead front may wash out in the western Gulf as another
attempts to reform around the low and take its place early next
weekend.

Fracasso


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