Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
418 PM EDT Sat Jul 28 2018

Valid 12Z Wed Aug 01 2018 - 12Z Sun Aug 05 2018

To commence the month of August, a mean ridge will be situated
over the eastern half of Alaska into the Yukon Territory. Within
the band of low-level amplitude upstream height falls, a more
pronounced upper trough will unfold which situates over the
northeastern Pacific during the Day 6-8, August 3-5 period. To its
west, an impressive closed high settles to south of the Aleutians
with 594-dm mid-level heights nearing the coastline. Relative to
climatology, this easily hits the 2 sigma range from Thursday
onward. There are signs of a northern erosion of this positive
height anomaly toward the conclusion of next weekend.
Amplification in the upstream flow, possibly due to a tropical
cyclone as shown by the 12Z/00Z GFS runs, would eventually lead to
this transition in the pattern. Farther north, a deep upper low
anchored over far northern sections of Nunavut will drive height
falls through eastern Alaska. This will ultimately bring an end to
a warm start to the week as highs on Wednesday over this section
of the state will reside in the low to possibly mid 80s.
Otherwise, the remainder of Alaska can expect daily chances for
showers and thunderstorms, particularly over the terrain.
Regarding the overall preference, found the forecast to be of
above average confidence given the level of amplification
unfolding. A combination of the 12Z GFS/00Z ECMWF with the 12Z
GEFS and 00Z ECMWF/NAEFS ensemble means was utilized throughout
the period with decreasing operational influences beyond Day
6/Friday.


Rubin-Oster


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