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Alaska Extended Forecast Discussion
(Caution: Version displayed is not the latest version. - Issued 1822Z Mar 16, 2018)
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Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
222 PM EDT Fri Mar 16 2018

Valid 12Z Tue Mar 20 2018 - 12Z Sat Mar 24 2018

...Clearing across the interior while unsettled conditions
continue across the Aleutians...

The guidance showed good agreement over and near Alaska this
period.  Due to this, the pressures and 500 hPa heights were based
on a 00z UKMET/00z ECMWF/06z GFS/00z Canadian blend early on
(Tuesday into Wednesday) before incorporating increasing amounts
of the 00z NAEFS/00z ECMWF ensemble mean solutions with time. 
This preference maintained good continuity in the 500 hPa and
pressure field.  The other grids were based on a 20% split of the
06z GFS, 12z GFS, 00z ECMWF, 00z ECMWF ensemble mean, and 00z
NAEFS mean.

A trough leaves eastern AK while ridging invades the west which
clears out the interior from Tuesday onward.  There remains a
strong guidance signal for low pressure over the Bering Sea
towards the Aleutians next week. Downstream energy propagation
will lead to moist flow with an unusually well organized
low/frontal system inland push offering widespread enhanced snows
into southwest Alaska. 

Undercutting triple point low development and height falls also
splits underneath to the Gulf of Alaska early next week to support
limited southern/southeastern Alaska precipitation and several
secondary cold surges into mid-late week as high pressure builds
over the interior. This is supported upstream as a deepening
low/active weather over the stormy western Bering Sea and
Aleutians mid-late next week acts to amplify downstream flow. 
This leads Gulf of Alaska closed mid-upper level trough/low
development with lower atmospheric frontogenesis response and
unsettled maritime conditions, though the details concerning the
strength of such lows and their number remains a question late
next week.