Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
308 PM EST Mon Feb 04 2019

Valid 12Z Fri Feb 08 2019 - 12Z Tue Feb 12 2019

...A series of storms to work from the Bering Sea into Western
Alaska...

...Guidance/Predictability Assessment and Weather/Hazards
Highlights...

Recent models and ensembles offer a reasonably similar larger
scale pattern evolution aloft at medium range time scales.
However, deterministic models do offer much more embedded surface
system timing variance than ensemble means. Accordingly, the WPC
Alaskan medium range product suite was primarily derived from a
blend of the latest and quite compatable GEFS/ECMWF ensemble
means. 

In this scenario, amplified flow is expected to persist from the
North Pacific to Alaska during the extended period. A mean trough
will persist across the western Aleutians and portions of the
Bering Sea, with downstream ridging from the Gulf of Alaska north
into mainland Alaska. A number of systems will rotate through the
mean Bering trough during the period, and ensemble means showed
relatively good consensus and continuity with the main systems.
One precipitation focusing frontal system should move from the
eastern Bering Sea into mainland Alaska into Fri/Sat. A second
precipitation focusing system follows fairly closely behind,
entering the Bering Sea Fri/Sat. A subsequent track over the
Bering Sea into western Alaska Sun/Mon acts to rebuild the
downstream interior ridge in the wake of the lead system. Timing
is less certain at longer time frames, but it seems a third main
progressive system may reach the Bering Sea in a week to again
reach western Alaska day 8/next Tue.

Schichtel


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