Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
321 PM EST Wed Jan 24 2018

Valid 12Z Sun Jan 28 2018 - 12Z Thu Feb 01 2018

The deep vortex over the State will steadily slide south into the
Gulf of Alaska this weekend, while upstream ridging builds in over
the Bering Sea.  Model guidance remains locked into the large
scale pattern during the medium range period, with both the
GEFS/ECMWF ensemble means advertising the upstream ridge building
to an expansive and largely anomalous (2.5-3.0 standard deviations
above normal) blocking high centered over far eastern Russia by
next Wednesday.  Models are also coming into better agreement with
the details of mid-level energy rotating around the deep vortex
and a strong Pacific low lifting through the Gulf of Alaska and
towards the Panhandle Sunday/Monday, but then model solutions
begin to diverge with the evolution of a possible elongated upper
trough aligning over the Aleutians next Tuesday/Wednesday.  

The WPC medium range forecast started with a blend heavily
weighted towards deterministic guidance in order to account for
some of the good model agreement with the smaller scale details,
but then the forecast transitioned to predominantly ensemble means
due to the diverging model solutions by Day 7-8.             


Gerhardt