Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
538 PM EST Wed Nov 11 2020
Valid 12Z Sun Nov 15 2020 - 12Z Thu Nov 19 2020
...Guidance/Predictability Assessment...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of best clustered guidance from the 12 UTC
GFS/ECMWF, 12 UTC GEFS/ECMWF ensemble means and the 19 UTC
National Blend of Models day4/Sunday. Opted to quickly transition
away from the GFS/ECMWF and toward the still compatible GEFS/ECMWF
ensemble means and the National Blend of Models days 5-8
(Monday-next Thursday) in a period of increasing forecast spread
and embedded system uncertainty, especially with offshore low
developments. WPC continuity was reasonably maintained overall
with this forecast strategy.
...Weather/Threats Highlights...
Above normal temperature should persist over the North Slope for
the next week and coastal western Alaska under upper ridging, but
meanwhile expect quite a cooling trend that will lead to below to
much below normal temperatures for much of the rest of the state
as an amplified upper trough settles from the Interior down over
the Gulf of Alaska. The upper trough favors unsettled conditions
including some enhanced precipitation, especially for the
Southeast Panhandle.
Upstream, systems traversing the Bering Sea/Aleutians early next
week will gradually weaken into the lead/amplified upper ridge,
but still present unsettled maritime conditions and some onshore
precipitation into western/northwestern Alaska.
There is then also an increasing guidance signal supporting new
upper trough/closed low development and approach into the Bering
Sea and Aleutians next Wednesday/Thursday that would bring a
threat of periods of enhanced winds/waves and precipitation across
the region then into western and southwestern/southern Alaska.
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:
- Much below normal temperatures across portions of mainland
Alaska, Sun-Tue, Nov 15-Nov 17.
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