Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EDT Mon Aug 23 2021
Valid 12Z Fri Aug 27 2021 - 12Z Tue Aug 31 2021
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of reasonably well clustered solutions from
the 12 UTC GFS/ECMWF/UKMET/Canadian Day4/Fri and then the
ECMWF/UKMET and ensemble means Day 5/Saturday. The
GEFS/NAEFS/ECMWF ensemble means seem much more run to run stable
into the days 6-8 period and are preferred amid quickly growing
model forecast spread and uncertainty.
...Pattern Overview and Weather/Threats Highlights...
Upper energies interacting with Arctic frontal boundaries will
support organized precipitation across northern and Interior
Alaska. In particular, an organized low pressure system tracking
to the north of the North Slope by Friday will bring increased
chances for enhanced precipitation inland across the North
Slope/Brooks Range and the eastern Interior. Additionally energies
rotating down from the Arctic Ocean will also favor organized
precipitation underneath into the North Slope into the weekend.
This pattern supports below normal maximum temperatures down
across much of Alaska.
Meanwhile to the south, an energetic system will track from south
of the Aleutians/AKpen Friday to the northeastern Gulf into next
weekend. This system offers a maritime threat along with some
enhanced weekend precipitation focus, mainly into Southeast AK.
Upstream, there is much more uncertainty with system development
and progression days 6-8 for Pacific systems working to the
Aleutians/Bering Sea.
Schichtel
Hazards:
- High significant wave heights for coastal portions of mainland
Alaska, Thu, Aug 26.
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