Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
535 PM EST Fri Nov 13 2020
Valid 12Z Tue Nov 17 2020 - 12Z Sat Nov 21 2020
...Guidance/Predictability Assessment...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of the now more compatible 12 UTC
GFS/ECMWF, 12 UTC GEFS/ECMWF ensemble means and the 19 UTC
National Blend of Models days 4-8. Despite improved forecast
clustering, especially with the larger scale pattern transition,
recent run to run model variance seems to only suggest near
average system predictability. Accordingly, inclusion in the
composite of the ensemble means was intended to mitigate some
model detail consistent with uncertainty.
...Weather/Threats Highlights...
The transition of an amplified upper ridge from the Bering Sea to
over the Interior will act to moderate temperatures there
significantly by early-mid next week and lead into a more benign
pattern over the region as precipitation focusing upper trough
energy lifting on the western periphery of this ridge lifts
through southwest then western/northwestern Alaska. Meanwhile,
lead upper troughing held underneath over an unsettled eastern
Gulf of Alaska and Southeast Panhandle will slowly weaken and lose
influence over the area.
Upstream, there is an increasing guidance signal supporting
amplified upper trough/closed low development into the Bering Sea
and Aleutians mid-later next week. This would bring a potentially
significant threat of enhanced winds/waves and precipitation
across the region, then increasingly later next week/weekend into
southwest and across southern Alaska as ample upper trough and
storm energies work into the Gulf of 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:
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