Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
342 PM EDT Mon Mar 12 2018

Valid 12Z Fri Mar 16 2018 - 12Z Tue Mar 20 2018

...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...

A blend of the reasonably compatable 12 UTC GFS and 00/12 UTC
ECMWF provides a reasonable starting point for the medium range
forecast period over Alaska and vicinity Friday. This solution in
particular maintains surface low integrity/continuity over
southwest Alaska as well as for a multitude of systems in active
lead flow over the interior/north slope and upstream over the
Bering Sea/Aleutians.

Model and ensemble forecast spread and implied uncertainty
increases significantly by the weekend and into next week. Prefer
an ensemble mean forecast approach and guidance from the 12 UTC
GEFS mean and 00 UTC ECMWF ensemble mean that seem to cluster best
for this uncertain period. 

In this scenario, arctic mid-upper level trough progression and
associated height falls should accompany frontal passage and some
modest snow potential from the North Slope down into the interior
Friday into the weekend. Underneath...lead energy splitting
eastward over the Aleutians Friday meanwhile works a modest
associated surface low/frontal system across the northern Gulf of
Alaska this weekend that would focus some enhanced precipitation
for southern and southeastern Alaska as enhanced over terrain.

The active pattern reloads further upstream where there is a
decent guidance signal for deep low development potentials over
the western Bering Sea headng through the weekend and into early
next week. Downstream propagation of energy may lead to some
enhanced flow into western Alaska and into the interior with low
approach. Undercutting triple point low development and height
falls then again work into the Gulf of Alaska early next week to
renew potential for another period of modest to locally terrain
enhanced southern and southeastern Alaska precipitation.

Schichtel