Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
253 PM EST Fri Feb 08 2019

Valid 12Z Tue Feb 12 2019 - 12Z Sat Feb 16 2019

...Major Bering Sea Storm Threatens Western/Northern Alaska Early
Next Week...

...Guidance Assessment...

The latest GFS/ECMWF and GEFS/ECMWF ensemble mean solutions
overall cluster reasonably well for next week. The WPC Alaskan
medium range forecast product suite was primarily derived from a
composite blend. However, applied increased blend weighting to the
ECMWF ensemble mean to maintain max WPC continuity and manual
adjustments were also applied to keep deepened offshore low
pressure depths and circulations that are more consistent with
favorable support aloft. 

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

The dominant system early-mid next week will still be a strong
storm tracking across the northwestern Bering Sea and then close
to the Bering Strait and northeastward into the Arctic. This storm
will likely bring strong winds/high waves and focused
precipitation from the Bering Sea/Aleutians into the western
mainland. The passage of this deep system will bring ample height
falls inland across the interior and North Slope down into the
Gulf of Alaska into a lead upper ridge extending from the
northeastern Pacific into Mainland Alaska/northwestern Canada.
Additional low/frontal system development will meanwhile slide
underneath over the northern and eastern Gulf of Alaska to produce
a modest precipitation swath into southern to southeastern Alaska.

Recent guidance still shows the main upper ridge will rebuild
westward later next week toward an axis over the western half of
the mainland. As this evolution occurs the pattern favoring
northeastward-moving lows over the northwestern Bering Sea,
progressive frontal passages farther south/east, and periodic Gulf
waves should transition toward one that keeps low pressure
confined more over the western half of the Bering Sea while high
pressure strengthens over the mainland and northwestern Canada.
These western to central Bering Sea lows have the potential to be
significant in the days 6-8 timeframe.

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