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Alaska Extended Forecast Discussion
 
(Latest Discussion - Issued 2006Z Jan 18, 2019)
 
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Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EST Fri Jan 18 2019

Valid 12Z Tue Jan 22 2019 - 12Z Sat Jan 26 2019

Longwave pattern still exhibits above average predictability with
increased upper ridging over western Canada and troughing through
the Bering Sea across the Aleutians. However, the embedded systems
of smaller scale show little predictability and continuity in
successive runs from any deterministic model, so confidence in
system timing/strength is low. Used the ensemble means (GEFS/ECMWF
ens mean) as a starting point though they even differed over the
Bering Strait with how to handle the upper trough/low as it
splits/combines/separates into two components north/south. Enough
agreement existed between the 12Z GFS and 00Z ECMWF early in the
period to use them as added detail to the forecast but both were
too different from each other and the means to trust beyond next
Thursday/Friday. End result is still the same -- 1) moderating
trend in temperatures with sustained southerly flow aloft that
should work its way to the surface eventually and 2)
increased/persistent rain/snow from Kodiak/Southcentral into the
Panhandle as fronts lose eastward progression. Secondary focus of
snow (maybe freezing rain?) will be over Southwest Alaska near the
favored surface low track.


Fracasso


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