Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 PM EDT Fri Oct 26 2018

Valid 12Z Tue Oct 30 2018 - 12Z Sat Nov 03 2018

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

The models and ensembles cluster with the initial low pressure in
the Gulf of AK weakening later Tue into Wed 31 Oct, with the slow
movement leading to a prolonged precipitation event, with lower
elevation rain and high elevation snow. Heavy amounts are expected
due to the long duration.

A break occurs on Wed in between systems, with the next low
developing south of the Aleutians and moving north.  The parent
low crosses the Aleutians Wed night to early Thu., with the low
weakening and triple point low developing east in the north
Pacific.  The latter low moves north Thu towards the south coast. 
The stronger system has potential to produce another heavy
precipitation even Thu/early Fri, depending on the timing. The
GEFS and ECMWF ensembles were blended in to the deterministic
forecast to mitigate timing differences.

To the northwest, ensembles persist toward more troughing over
northeastern Russia which may push a cold front into NW Alaska.
The front drifts slowly east while the next cyclone develops and
moves south of the Aleutians Fri 02 Nov, and possibly over the
Aleutians or adjacent coastal waters Sat 03 Nov.  A multi-Gfs and
ECMWF deterministic and ensemble mean GEFS/ECMWF mean blend was
used following a general cluster of solutions until better
clustering develops later.

Temperatures are forecast to be near to above average with 700 mb
temperature anomalies generally 0.5-1.5 std deviations above
normal mid to late next week.

Petersen


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