Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
656 PM EST Mon Nov 15 2021
Valid 12Z Fri Nov 19 2021 - 12Z Tue Nov 23 2021
...Much below normal temperatures likely across Alaska through the
medium range period...
...Overview and Guidance Evaluation/Preferences...
The latest suite of guidance continues to have above average
predictability with the expansive blocky pattern over Russia and
areas west of the Mainland, keeping a mean trough near/south of
the Aleutian Chain through the extend period. The degree of
clustering among the global guidance through about 00Z 21 November
lends to above average confidence on this pattern evolution.
However, beyond this time the degree of spread increases. The 12z
GFS, ECMWF, and CMC continue to show reasonable agreement with the
large scale pattern for a purely deterministic model blend days
4-5. The ensemble means were included for in increasing weights
through the end of the forecast period. This model blend helped
maintain continuity from the previous issuance.
...Weather/Hazard Highlights...
Through the extend period the precipitation will mainly be focused
over the southern coastal areas, the Southeast and along the
Aleutian Chain. Elsewhere, very cold temperatures and dry
conditions will persist. As the surface low moves through the Gulf
through Friday there will be periods of moderate to heavy
precipitation over the the Panhandle region. This pattern also
favors flow funneling through the mountain ranges of southern
Alaska; which may lead to strong outflow winds across Southwest
Alaska. Wet and unsettled conditioned will return as another
system tracks into the Aleutians late in the period, spreading
from the Aleutians to locations along the southern coast and
enhancing over the Panhandle by next weekend.
Much below normal temperatures should prevail across much of
Alaska, especially the central and southern regions, through next
week as surface high pressure becomes established across the
state. The most pronounced anomalies should be over the western to
southern part of the state where daytime highs could be as much as
20-30+ degrees below normal. The temperatures are expected to stay
cooler than average, although they may moderate as the synoptic
flow becomes less amplified. The North Slope will likely remain
near, or briefly above seasonal normal through the extended period.
Campbell
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
- Heavy precipitation across portions of the Alaska Panhandle,
Sun-Mon, Nov 21-Nov 22.
- Much below normal temperatures across portions of mainland
Alaska, Thu-Mon, Nov 18-Nov 22.
- Much below normal temperatures across portions of mainland
Alaska, Thu-Fri, Nov 18-Nov 19.
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