Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
336 PM EDT Wed Oct 24 2018

Valid 12Z Sun Oct 28 2018 - 12Z Thu Nov 01 2018

...Heavy precipitation for much of the Panhandle...

Ensembles remain in good agreement on the developing Pacific upper
pattern that will feature building heights off California toward
the Gulf of Alaska as well as over Siberia. This will favor
pulling the trough axis westward past the Dateline with successive
systems next week. The deterministic models continue to struggle
with how to eject the system located south of the Aleutians on
Sunday/Monday as the triple point likely races northeastward,
modulated by the northern upper low over NW Alaska. Consistency
has been lacking in timing/strength but it seemed that the 00Z
GFS/ECMWF clustered decently with the 06Z GEFS and 00Z ECMWF
ensemble mean by Tue/Wed, so a blend of those inputs was used as a
starting point. A more significant upper low will move off
Kamchatka next ~Wed or so and approach the Aleutians by the end of
the period, acting to tug the upper trough westward as a trailing
system to its west lifts north toward the AKPen. The pattern
supports several inches of rain and higher elevation snow for the
Panhandle with several days of SW upper flow and the initial (Sun)
and next (Tue/Wed) systems. Both the National Blend of Models and
in-house ensemble bias-corrected QPF yield over 5" of QPF in
favored areas with maxima nearly twice that. Temperatures are
forecast to be near to above average despite the troughing over
the interior as heights remain near above average as well.

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