Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
735 PM EDT Fri Sep 18 2020
Valid 12Z Tue Sep 22 2020 - 12Z Sat Sep 26 2020
...Overview and Guidance/Predictability Assessment...
The spread with today's model guidance increased in comparison to
the last few cycles, struggle to lock on to any one track. The
consensus agrees a robust low will track from the Bering to the
Gulf early in the week and eventually track toward the Panhandle.
A few suggest an Arctic trough plunges into the Bering/western
Alaska behind this low, which would affect the strengthen/movement
of this low by the later periods. Given the uncertainty, opted to
initialize with a general blend of the 12Z EC/GFS/CMC/UK as
clustering were pretty good for Monday. Beyond that, the EC
mean/GEFS mean/NAEFS were included Tuesday to the end of the
forecast to reduce the spread.
...Weather/Threats Highlights...
Lingering clouds and showers across parts of the southern Mainland
and Panhandle as a weak front passes. A more robust low pressure
system crossing the Aleutians into the Gulf will spread heavy
precipitation from the central Aleutian Chain, all along the
southern coastal areas Monday and Tuesday, shifting to the
Southeast Tuesday and Wednesday. Stronger winds will also
accompany this low as it exits the Bering and tracks into the
Gulf. With the low hanging around in the Gulf, high winds are
expected Tuesday and Wednesday for portions of the Southeast. Much
of the southern coastal areas and the North Slope will have
maximum daily temperatures near or below average through the
extended period while much of the Interior will observe above
average temperatures.
Campbell
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:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Mon-Tue, Sep 21-Sep 22.
- Heavy precipitation across portions of the Alaska Panhandle,
Tue-Wed, Sep 22-Sep 23.
- High winds across portions of the Alaska Panhandle, Tue-Wed, Sep
22-Sep 23.
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