Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 PM EST Tue Feb 06 2018

Valid 12Z Sat Feb 10 2018 - 12Z Wed Feb 14 2018

...Guidance and Predictability Assessment...

Todays WPC Alaskan medium range product suite was mainly derived
from a composite of the reasonably compatable 00 UTC GEFS/ECMWF
ensemble means days 4-8. Leaned weighting in favor of the ECMWF
ensemble mean in this blend to better match embedded system trends
of the deterministic models. To that end...also included input the
00 UTC ECMWF in the days 4-6 timeframe in a period of better
forecast clustering. This scenario maintains good WPC product
continuity from yesterday and includes some enhanced detail
consistent with near average forecast spread and  predictability
in this pattern. The newer 12 UTC ECMWF offers reasonably similar
guidance to the 00 ECMWF UTC run this week, while the 12 UTC GFS
has less broad ensemble support and slightly less run-run
continuity versus the 00/06 UTC GFS.  


...Pattern Overview and Weather Highlights/Threats...

Amplified mid-upper ridging extending from the eastern Gulf of
Alaska inland over the interior/North Slope is expected to
breakdown this weekend with steady approach of an energetic
Aleutians closed trough aloft and an associated surface low and
frontal system. The approach/height falls and increased lead
moisture inflow should support widespread and locally enhanced
precipitation from the Aleutians and southwestern Alaska and
maritime interests in proximity of the main low, more in ernest
into southern/southeastern Alaskan with sustained lead flow and
also with some emphasis into the interior into early next week.
There is then later period potential for secondary low approach
and organized weather potential to lift into the northern Gulf of
Alaska to again effect southern and southeastern portions of the
state, but uncertainty seems greater with this system. There is
some guidance signal for renewed upstream flow amplification into
next midweek with potential development and slow approach of a
deepened low off Asia and into the Bering Sea.

Schichtel