Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
219 PM EST Fri Nov 09 2018
Valid 12Z Tue Nov 13 2018 - 12Z Sat Nov 17 2018
Upstream flow over northeastern Russia will feature the most
stable height anomaly (ridging and/or a closed upper high) that
favors downstream troughing over Alaska. However, the flow is
complicated by shortwaves atop the ridge diving through the Bering
Sea coupled with mid-latitude flow from the central Pacific. The
ensembles were in good agreement though the ECMWF ensemble mean
was much better defined than the GEFS mean. Given the pattern that
supports phasing of streams and deeper surface systems (though not
a given), preferred the ECMWF ensemble mean through the period.
The 00Z ECMWF fell mostly in line with the means and was used as
the deterministic weight for added details, despite the rather
inconsistent forecasts. The GFS again seemed to quick and too far
from the ensemble consensus to use through the period. The 00Z
Canadian was in agreement with the ECMWF in most places but on its
own in others, so it was not used but added some background
support for the ECMWF. Overall confidence was no better than
average with the individual systems though at least in the broad
sense there is good agreement on their synoptic existence.
Precipitation potential will shift eastward away from Southcentral
and toward the Panhandle midweek as a strong southerly influx of
moisture along/ahead of the lead system moves into western Canada.
However, next system later in the week will bring in another round
of rain/snow to the Panhandle as it lifts into the Gulf.
Temperatures will trend colder in time over most of the state,
especially the interior, from above average to below average.
Blend of the NBM and ECMWF ensemble mean proved to be a useful
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can be found at: