Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
750 PM EDT Thu Sep 17 2020
Valid 12Z Mon Sep 21 2020 - 12Z Fri Sep 25 2020
...Overview and Guidance/Predictability Assessment...
A surface low and its associated cold front will be lifting into
the southern Mainland/Southeast Sunday and Monday. Another low
will deepen as it drops from the Bering, across the Aleutians into
the central Gulf of Alaska. This system is forecast to be
well-defined and wrapped up as it tracks toward the Gulf. Heavy
precipitation is expected ahead of the front and areas north of
the central low pressure Monday and Tuesday, particularly northern
portions of the Aleutian Chain and much of the southern coastal
areas. The system will advance to the east spreading heavy rain to
the panhandle Tuesday through Thursday. Additionally, high winds
will be possible during this time from approximately southern
portions of Baranof Island to the Dixon Entrance as the front
slows and remains in the Gulf.
The GFS is favoring a slight southern trend with the low crossing
from the Aleutians to the Gulf- the EC and the ensemble means are
fairly close to its track, while the CMC persists in being faster
than the cluster. The spread increases on Tuesday/Wednesday as the
models struggle with the evolution of the system, however convenes
by late Wednesday/Thursday. The preferred blend is the 12Z EC/GFS
and their means with light weighting of the CMC.
ensemble.
...Weather/Threats Highlights...
Lingering clouds and showers are possible across parts of the
southern Mainland and panhandle as a front moves into Canada early
in the period. Increased cloudiness, heavy precipitation and
increasing gusty winds will accompany a fairly progressive low
pressure system as it tracks across the Bering, the Aleutians and
into the Gulf of Alaska next week. Much of the southern coastal
areas and the North Slope will have maximum daily temperatures
near or below average through at least mid week, 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 mainland Alaska, Mon-Tue,
Sep 21-Sep 22.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Tue-Wed, Sep 22-Sep 23.
- Heavy rain across portions of the Alaska Panhandle, Tue-Thu, Sep
22-Sep 24.
- 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