Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
314 PM EDT Tue Mar 13 2018

Valid 12Z Sat Mar 17 2018 - 12Z Wed Mar 21 2018

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

Medium range model and ensemble forecast spread and implied
uncertainty has decreased a bit today, bolstering confidence a bit
for at least mid-larger scale features. The latest several ECMWF
runs and recent GEFS/ECMWF ensemble means in particular seem
compatable/well clustered through the weekend and even to a lesser
degree through early next week. Accordingly...prefer a blended
forecast solution using these guidance pieces whose resultant
output maintains decent WPC continuity.

In this scenario, arctic mid-upper level trough progression and
associated height falls will accompany frontal passage and modest
snow potential from the North Slope down into the interior this
weekend. Underneath...lead energy splitting eastward meanwhile
leads to a modest surface low/frontal system in the northern Gulf
of Alaska this weekend to support some southern and southeastern
Alaska precipitation.

The active pattern reloads further upstream where there is a
strong guidance signal for deep low development potentials over
the Bering Sea this weekend into early next week. Downstream
propagation of energy may lead to some enhanced flow into western
Alaska and the interior/North Slope as per low and frontal system
approach. Undercutting triple point low development and height
falls also splits underneath to the Gulf of Alaska early next week
to renew potential for another period of modest to locally terrain
enhanced southern and southeastern Alaska precipitation.

Yet another deep low could be brewing upstream over the western
Bering Sea heading into the middle of next week that could act to
overall amplify the flow downstream.

Schichtel