Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
245 PM EDT Thu Aug 16 2018

Valid 12Z Mon Aug 20 2018 - 12Z Fri Aug 24 2018

An upper low will lift through the AKPen into Southcentral early
next week as another one in the Bering Sea moves slowly but
steadily eastward. To the north, the models/ensembles show little
consensus on how to handle the relaxation of upper ridging and the
possible intrusion/deposition of compact upper lows from the north
as an upper low shifts east through the Canadian archipelago.

For the areas south of 65N, the 12Z GFS and 00Z ECMWF clustered
well with the 00Z ECMWF ensemble mean and mostly with the 06Z GEFS
mean, so a blend of that group served as a good starting point
that also kept good continuity. By late next week, timing
differences expand over the eastern Bering through the Gulf though
a trend toward a slower and more amplified solution maybe taking
shape due to the upstream (W Pac) evolution including the track of
current Tropical Storm (and likely future Typhoon) Soulik very
near southern Japan in five days. For northern areas, heights are
forecast to fall as the upper ridge weakens which would allow at
least weak troughing to take its place and potentially an upper
low per some models (ECMWF especially). Confidence is low in such
a solution but it is certainly plausible.

The pattern will be rather active through the Aleutians eastward
to the Panhandle with multiple bouts of precipitation and few dry
periods. Temperatures are forecast to be below average to the
north and south but near to perhaps a bit above average through
the interior.

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