Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
514 PM EST Thu Nov 18 2021
Valid 12Z Mon Nov 22 2021 - 12Z Fri Nov 26 2021
...Below normal temperatures, high winds and heavy precipitation
expected across portions of Alaska through the medium range
period...
...Overview and Guidance Evaluation/Preferences...
The models agree that the longwave trough will remain in place
over Alaska however there is increasing noise on the exact
location, strengthen and timing of individuals impulses within
this flow. Through the extended forecast the CMC and UKMET are
favoring a slower progression while the ECWMF and the GFS are
faster, however the GFS takes a track further south. The ensemble
means are fairly close to their parent solutions but are not as
amplified as to be expected. This degree of spread results in a
lower confidence forecast but the impacts will keep stronger winds
across the southern part of the state along with periods of
moderate to heavy precipitation. The initial starting point of the
forecast relied on the a blend of the 12Z ECWMF/GFS/UKMET/CMC and
included more weights of the ensemble means through the middle and
late periods to help dampen the noise in the models.
...Weather/Hazard Highlights...
Temperatures are expected to be below or much below normal for a
vast majority of the state through the extended forecast. The
North Slope will likely remain near, or briefly above seasonal
normal through the extended period. Numerous locations observing
daily readings as much as 20-30+ degrees below normal. Much of the
Interior will have drier conditions while there will be multiple
rounds of precipitation, possibly heavy at times, across the
Aleutian Chain, the southern coast and the Panhandle. This pattern
will also favor flow funneling through the mountain ranges of
southern Alaska; which may lead to strong outflow winds.
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, Nov 21.
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Sun-Mon, Nov 21-Nov 22 and Wed-Thu, Nov 24-Nov 25.
- Much below normal temperatures across portions of mainland
Alaska, Sun-Tue, Nov 21-Nov 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