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Alaska Extended Forecast Discussion
 
(Latest Discussion - Issued 1906Z Nov 15, 2018)
 
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Abbreviations and acronyms used in this product
 
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Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
206 PM EST Thu Nov 15 2018

Valid 12Z Mon Nov 19 2018 - 12Z Fri Nov 23 2018

The overall synoptic pattern across Alaska for the Day 4 (Monday)
to Day 8 (Friday) time period features initial troughing in the
Gulf on Day 4, which essentially becomes reinforced by one system
entering the Bering Sea Day 5-6, and another one crossing the
Aleutians day 7-8. Upper ridging across the mainland on Monday
weakens through the week as multiple systems slide in underneath.

There is decent agreement in the beginning of the period between
the 06z GFS and 00z ECMWF along with the ensemble means with the
overall synoptic pattern. By day 6, differences in both timing and
details of individual systems/closed lows begin to arise in the
operational models which results in various depths/placements of
surface lows crossing the Aleutians into the Gulf/southern
mainland. Despite some minor timing differences, there is fairly
good agreement through the period between the latest runs of the
GEFS/ECENS/NAEFS ensemble means. The blend for this cycle of the
WPC Alaska 500mb and pressure/fronts progs uses a mostly
operational GFS/ECMWF blend on day 4, with a mostly ensemble mean
blend (between the GEFS/ECENS/NAEFS) from day 5 onward. This
overall blend gave a forecast very close to yesterdays continuity
as well.

Regarding sensible weather impacts...heavy rainfall will linger
along the Panhandle region early in the week, with additional
rounds of organized to possibly locally heavy rains moving across
the Aleutians, the southern coast, and eventually the Panhandle
again mid to late week. Upper-level ridging should keep
temperatures above normal for interior portions of the state, with
a return to near normal values by the end of the week.

Santorelli

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