Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 PM EST Sun Dec 05 2021
Valid 12Z Thu Dec 09 2021 - 12Z Mon Dec 13 2021
...Another Major Storm for Alaska...
...Overview and Guidance Evaluation/Preferences and Weather/Hazard
Highlights...
Amplifying upper trough energies will support deep southern Bering
Sea storm genesis into Thursday, with model guidance dropping low
system pressure into the 950's mb. This system presents a
significant maritime and Aleutian wind, wave and wrapping
precipitation threat. The powerful storm is slated to slam into
southwest Alaska, the Alaskan Peninsula, Kodiak Island and
southern Alaska Thursday into Friday. Downstream translation and
northern Gulf triple point low redevelopment Friday into next
weekend will act to threaten the region with high winds and
offshore waves along with heavy precipitation onward into
southeast Alaska through next weekend.
12 UTC GFS/ECMWF solutions seem best clustered days 4-6 (Thu-Sat),
but offer storm timing and energy transfer differences back over
the Bering in particular for days 7/8. Accordingly opted to shift
WPC forecast focus increasingly from the GFS/ECMWF to the
GEFS/ECMWF ensemble means at these later time frames in a period
with rapidly decreasing predictability. That said, there is a
decent guidance signal to support additional deep Bering Sea storm
genesis at these less certain longer time frames to monitor.
Schichtel
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
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