Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 PM EST Sun Feb 04 2018

Valid 12Z Thu Feb 08 2018 - 12Z Mon Feb 12 2018

Predictability decreases quicker with the latest models compared
to previous days as the ensembles are having trouble resolving the
flow out of northeastern Asia in the short term (around Tuesday).
In addition, the longwave pattern itself, though predictable in
the day 4-5 range, remains much less predictable with individual
systems. As such, used a blend of the recent GFS/ECMWF guidance
with their ensemble means to start the forecast (Thu-Fri) as a
system pushes through the Bering into western Alaska and the
eastern Aleutians before dissipating. Strength/orientation of the
upper ridge axis is still a bit in question, but should mostly
hold the systems to the open waters as they weaken to the
north/east.

By next weekend, had to use an ensemble mean blend as no
deterministic model seemed to fit even the much less defined mean
trough locations. This at least kept good continuity from
yesterday with two systems dissipating and lifting northeastward
Fri-Sat and then another coming out of the north Pacific Sun-Mon.


Fracasso