Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
212 PM EST Fri Nov 23 2018

Valid 12Z Tue Nov 27 2018 - 12Z Sat Dec 01 2018

...Guidance/Predictability Assessment...

Operational models and individual ensemble members continue to
show significant spread for features within an overall evolution
depicted similarity in the ensemble means. On day 4 (Tue), there
is decent consensus among the ensemble means that a decaying
surface low will be located near Kodiak Island, with a weakening
surface front pushing onshore in southern/southeastern Alaska.
Deterministic solutions continue to show a large degree of
run-to-run variability with the details of this system, showing
the potential for multiple waves of low pressure/triple point lows
evolving quickly. Ensemble mean solutions have maintained a much
higher degree of consistency, and thus they remain the preference.
The active pattern continues with another system expected to track
near/south of the Aleutians and Alaska Peninsula by mid to late
next week, and yet another entering the western Bering Sea late
next week. The same story holds true with these systems, in that
individual model solutions show a wide degree of spread and
variability, while ensembles show a bit more consistency.
Ensembles show some consensus that the late week system entering
the Bering Sea could be a bit stronger, with even a blend of
ensemble means resulting in a surface low in the well into the
980s (hPa). Given these considerations, this forecast maintains
near exclusive focus on the ensemble means, which yielded a
forecast close to continuity.


...Sensible Weather Highlights/Hazards...

Locally heavy precipitation will be possible on Tue as the low
weakens in the Gulf and the surface front moves onshore.
Persistent onshore flow in the wake of the front will keep
precipitation chances relatively high across southern/southeastern
Alaska through much of next week. Precip should become more
widespread across the Aleutians by late next week in association
with the next couple low pressure systems traversing the North
Pacific. Temperatures during the extended period will generally be
several degree above average south of the Brooks Range, as the
active North Pacific flow regime will inhibit any significant
incursions of arctic air farther south.


Ryan

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