Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 PM EST Mon Feb 25 2019

Valid 12Z Fri Mar 01 2019 - 12Z Tue Mar 05 2019

The strong upper high will continue to be a dominant feature over
eastern Alaska through the medium range period. A mean trough will
bring different systems entering the Bering Sea and moving through
the Aleutians/toward southwestern Alaska throughout this time
period.

The first system approaching the southwest Alaska on Day 4/Fri
will weaken as it moves toward the coast. However, the next system
will quickly follow. With this occluded low, the 12Z GFS was much
faster than the 00Z ECMWF--and the ECMWF lines up much more with
the 00Z ECMWF ensemble mean/06Z GEFS mean, and the 00Z CMC/UKMET.
The front will begin to sweep across the Aleutians by Day 6/Sun
through Tue. As the surface low moves north and east, it will
weaken--entering the Chukchi Sea later on Mon into Tue. Once
again, the 12Z GFS was so fast and was clearly an outlier from the
other guidance. The 00Z ECMWF and the 00Z ECMWF ensemble mean/06Z
GEFS mean matched up quite well in regards to the position of the
surface low from Days 6-8/Sun-Tue. Thus, WPC based a blend on the
00Z ECMWF/12Z GFS from Days 4-5, increasing the ensemble means and
not using the 12 GFS from Days 6-8.

Most of the state will remain precipitation-free under the upper
high--with rain/snow confined to the Aleutians and western Alaska.
Temperatures will be mostly above average through the medium range
period but variable through the interior. The greatest temperature
anomalies will likely occur across the North Slope into
northwestern Alaska where temperatures may exceed 25-35 deg F
above average owing to sustained southerly flow over lower/flatter
elevations. Temperatures over the Panhandle will be slightly below
average due to northeasterly/easterly flow out of Canada,
especially next weekend and into next week as the upper high slips
northward and allows a cool push of air to leak southwestward out
of the Yukon.

Bullet points from the WPC Days 3-7 Hazards chart:
https://www.wpc.ncep.noaa.gov/threats/threats.php

High winds across portions of mainland Alaska, Thu, Feb 28.
High significant wave heights for coastal portions of mainland
Alaska and the Aleutians, Thu, Feb 28.
High significant wave heights for coastal portions of the
Aleutians, Sat-Mon, Mar 2-Mar 4.


Reinhart


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