Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
218 PM EST Sun Nov 18 2018

Valid 12Z Thu Nov 22 2018 - 12Z Mon Nov 26 2018

The overall synoptic pattern across Alaska for the Day 4
(Thursday) to Day 8 (Sunday) time period features initial upper
troughing in the Gulf and over Alaska with upper level ridging
buidling back in by the weekend. A series of shortwaves/closed
lows break off from broad troughing over eastern Russia sending
surface low pressure systems south of the Aleutian island chain.

There is actually fairly good agreement on the overall synoptic
pattern through much of the period between the operational
GFS/ECMWF and their respective means. As has been the case for
several days in a row now, differences in both timing and details
of individual systems/closed lows begins to arise after about day
5 in the operational models. This results in varying
strength/placements of surface lows tracking near or south of the
Aleutians. There remains some differences in the timing of ridge
rebuilding across the Gulf and southern Alaska days 6-8 with the
operational GFS the slowest and the operational CMC the quickest.
The 00z ECMWF sits in the middle of these two solutions and is
very close to that of the ensemble means as well. The blend for
this cycle of the WPC Alaska 500mb and pressure/fronts progs used
a majority GFS/ECMWF blend for days 4-5, with increasing weighting
of the ensemble means through the remainder of the period. Did
prefer a slight weighting towards the ECMWF as that seemed to
match the ensemble means the best. The overall forecast pattern
also maintains good continuity with yesterdays forecast.

Regarding sensible weather impacts...an overall drying pattern is
expected across most of the state through next weekend with
lingering showers possible across the Panhandle region. Systems
tracking south of the Aleutians and into the Gulf should bring
another round of rain, locally heavy possible, to much of the
southern coastline and eventually the Panhandle by early next
week. Temperatures should return to near or below normal at the
end of this week and into next weekend. Upper level ridging begins
to build back in across the southern half of the state by Day 7-8,
so another warm up can be expected across the southern third to
half of the state, while below normal temperatures are likely to
continue across northern Alaska underneath of persistent upper
level troughing.

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