Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1255 PM EST Fri Nov 30 2018

Valid 12Z Tue Dec 04 2018 - 12Z Sat Dec 08 2018

...Guidance/Predictability Assessment...

The latest GFS/ECMWF and GEFS/NAEFS/ECMWF ensemble guidance is
reasonably well clustered into Tuesday, but growing smaller scale
embedded system variance in the models favors usage of just the
ensemble means through the rest of next week (Days 5-8), with an
emphasized ECMWF ensemble mean providing max system continuity.

...Pattern Overview and Weather Highlights/Hazards...

The WPC Alaskan medium range period starts Tue with an energetic
shortwave lifting over the North Slope/Arctic overtop an interior
Alaskan upper ridge along with a swath of exiting snow. This ridge
rebuilds in the wake of shortwave passage to maintain the rest of
next week. An upstream closed upper level low will meanwhile slide
along the Aleutians Tue/Wed along with a deep surface low,
possibly ~970 mb. There is a threat of heavy rainfall for
southwest AK (especially for coastal locations) as a lead front
will also be slow to push eastward due to downstream ridging.
Southerly moist flow into southern AK will also fuel widespread
precipitation as enhanced by slow deep surface low appraoch. The
low and precipitation potential weakens/lifts northward to the
eastern Bering Sea/western AK around the rebuilt blocking ridge
centered over the mainland/Southeast AK. System genesis well
underneath will then work into the Gulf of Alaska late next week
into next weekend to support stormy conditions/heavy precipitation
potential for maritime interests and inland into the southern
Alaskan tier, but with the bulk of supporting energies aloft
tending with time to focus to the south of the state.

Schichtel


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