Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
221 PM EST Wed Feb 13 2019

Valid 12Z Sun Feb 17 2019 - 12Z Thu Feb 21 2019

Two positive height anomalies at 500mb--the first over
northeastern China and the second just south of the Gulf of
Alaska--will favor a quasi-zonal flow across Alaska with lower
heights centered over northeastern Russia. This will favor a storm
track across the Aleutians, through the Bering, into southwestern
Alaska and Southcentral, then through the Gulf into the Panhandle.
It's a fairly wet pattern for areas along 60N. The 12Z GFS and 00Z
ECMWF again paired fairly well with the 06Z GEFS and 00Z ECMWF
ensemble means (especially compared to earlier GFS runs), and a
mostly deterministic blend was used given better than average
confidence in the first couple days of the forecast period. This
will take a potent storm through the Bering Sea then across the
Gulf as it weakens atop the ridge. A lead system in the Gulf
Sunday will bring initial rain/snow to the Panhandle before the
trailing larger system. By next Wed/Thu, ensembles still struggle
to agree on the evolution off eastern Asia south of Japan given
the blocking to the north. For now, split the difference between
the GEFS/ECENS means which usually minimizes daily shifts in the
forecast progs. Upper pattern supports another system into the
Bering then toward southwestern Alaska midweek.


Fracasso


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