Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
709 PM EDT Mon Mar 22 2021
Valid 12Z Fri Mar 26 2021 - 12Z Tue Mar 30 2021
...Stormy pattern for Alaska...
...Guidance/Uncertainty Assessment...
The 12 UTC ECMWF/UKMET seem better clustered with 12 UTC
GEFS/ECMWF ensemble means and WPC continuity from yesterday than
the newly upgraded 12 UTC GFS and the 12 UTC Canadian. The WPC
Alaskan medium range product suite was primarily derived from a
composite blend featuring the 12 UTC ECMWF/UKMET days 4-5
(Friday-Saturday) before opting for the 12 UTC ECMWF and
increasingly the 12 UTC GEFS/ECMWF ensemble means days 6-8
(Sunday-next Tuesday) amid growing forecast spread and decreasing
forecast confidence. The 19 UTC NBM was downplayed today as it
contains significant 12 UTC GFS/Canadian input.
...Weather/Hazards Highlights...
A series of potentially strong storms are slated to effect Alaska
over the next week. Expect a Bering Sea system with uncertain but
favorable upper support and organized precipitation/winds to reach
the mainland Friday and work inland into the interior into the
weekend, but ample downstream energy transference will meanwhile
increasingly focus storminess into the northern then eastern Gulf
of Alaska and spread terrain enhancing precipitation into southern
and especially southeast Alaska. Upstream, a potentially
deep/powerhouse low is expected to emerge back into the Bering Sea
over the weekend and provide a significant maritime and Aleutians
threat. The storm is expected to reach/spread unsettled conditions
in earnest over much of the mainland and into the Gulf of Alaska
by late weekend and through early next week. This could include
enhanced wrapping precipitation and winds.
Schichtel
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat, Mar 27.
- High winds across portions of mainland Alaska and the Aleutians,
Sun-Mon, Mar 28-Mar 29.
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
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