Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
104 PM EST Mon Dec 24 2018

Valid 12Z Fri Dec 28 2018 - 12Z Tue Jan 01 2019

...Alaskan Heavy Precipitation Threat...

...Guidance/Predictability Assessment and Preferences...

Model and ensemble forecast clustering in this stormy/wet pattern
has improved a bit compared to the past few days so prefer a
composite blend of the latest GEFS/NAEFS/ECMWF ensemble means
along with smaller input from the latest GFS/ECMWF and National
Blend of Models for better system details consistent with
predictability.


...Weather/Threats Highlights...

A leading series of low pressure systems/fronts will track south
of the Alaskan Peninsula to the northern Gulf of Alaska into the
weekend. These lows present a maritime hazard in the form of high
winds/wave and heavy precipitation threat from the AK
peninsula/Southwest Alaska through southern/southeastern Alaska.
Individual system timing/strength remain variable in guidance, but
the overall storm track remains reasonable. The threat will be
enhanced into coastal communities and with heavy snows over
favored southern tier terrain. Expect mainly cold and dry
conditions overtop in this pattern for the North Slope/Interior
during this period, but uncertain shortwave energy aloft may
support some light snows. There is meanwhile an increasingly
strong days 4-8 guidance signal for flow amplification to include
development of a large closed low/trough aloft to favor
development of deep surface lows and stormy conditions for the
Aleutians/Bering Sea, with effects and hazards spreading to the
Alaskan Peninsula, southwest Alaska, the western Interior and
southern Alaska into 2019.

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