Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
431 PM EST Sat Dec 04 2021
Valid 12Z Wed Dec 08 2021 - 12Z Sun Dec 12 2021
...Deep and Dangerous Alaskan Lows next week...
...Overview and Guidance Evaluation/Preferences and Weather/Hazard
Highlights...
A deepened lead low working across the northern Gulf of Alaska
presents a lingering maritime threat over the region along with a
threat for locally heavy coastal rains and terrain enhanced heavy
snows over the Southeast Panhandle through midweek.
Meanwhile, upstream energy transfer over the Bering Sea will bring
another low pressure system and an enhanced wind and snow threat
focus back into western and southwestern Alaska midweek.
Subsequent and amplifying upper trough energies tracking to the
Bering Sea on the heels of this system by later seem increasingly
likely to support deep southern Bering Sea storm genesis into
Thursday, with some model guidance dropping low system pressure
below 950 mb. This system presents a significant maritime and
Aleutian wind and wave and wrapping precipitation threat. The
powerful storm is slated to slam into southwest Alaska, the AKpen
and southern Alaska Thursday into Friday. Downstream translation
and northern Gulf triple point low redevelopment Friday into next
weekend with act to threaten the region with high winds and
offshore waves along with heavy precipitation onward into
southeast Alaska.
Forecast spread has improved through medium range time scales and
the signal has increased for quite an active storm pattern next
week, bolstering forecast confidence. Details from the 12 UTC
ECMWF seems to be best clustered with GEFS/ECMWF ensemble means
and WPC continuity. Prefer a composite favoring the ECMWF day 4-6
(Wednesday-Friday), then increasingly the ensemble means into days
7/8 for next weekend.
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