Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
703 PM EDT Fri Oct 09 2020
Valid 12Z Tue Oct 13 2020 - 12Z Sat Oct 17 2020
...Overview and Guidance/Predictability Assessment...
A blend of reasonably compatible guidance from the 12 UTC
GFS/ECMWF and 12 UTC GEFS/ECMWF ensemble means was primarily used
to provide a starting point for the WPC Alaskan medium range
product suite. Most weighting in the blend was applied to the
ECMWF Tue/Wed and then increasingly the ECMWF ensemble mean amid
growing forecast spread and uncertainty. Emphasis on the ECMWF
then ECMWF ensemble mean shifted the blend into the more amplified
side of the full envelope of solutions for Alaska upper troughing.
This collaborative solution seems prudent given high upper ridge
amplitude upstream in most guidance. This maintains reasonable WPC
continuity.
...Weather/Threats Highlights..
Strong upper ridge amplification is expected up through the Bering
Sea to into the Arctic Ocean early next week. This should allow
Arctic flow energy to carve out an amplifying downstream upper
trough down over an increasingly unsettled and cooled/locally
snowy North Slope and Interior through mid-later next week before
the moderating main upper ridge is slated to shift eastward and
inland. Guidance is still quite varied with the details of the
upper troughing though, so details will emerge into shorter range
time scales. This Arctic energy may also amplify sufficiently to
overcome early-mid week southern stream troughing/systems over the
Gulf of Alaska. Coastal areas of southern and southeast Alaska
will remain unsettled/showery in this transitional pattern. The
Aleutians may turn more stormy late period as new upper trough
energies offer potential to work deepening systems into the region
as the main upper ridge shifts eastward.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
Hazards:
No significant hazards are expected over Alaska during this
forecast period.
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html