Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
745 PM EDT Thu Oct 21 2021
Valid 12Z Mon Oct 25 2021 - 12Z Fri Oct 29 2021
...Overview and Guidance/Predictability Assessment...
The medium-range period will likely begin with a cyclone center
passing quickly eastward to the south of the Alaska Peninsula
early next Monday. Model solutions have converged quite a bit
since yesterday but there is still a sizable east-west/timing
spread regarding the cyclone track. A general model compromise
yielded a track slightly to the south of yesterday's forecast. In
addition, it appears that the 06Z GFS rather than the 12Z run is
more compatible with the overall ensemble means for next Monday.
Beyond this time-frame, the ensemble means generally agree that a
broad cyclonic circulation will meander over the Gulf of Alaska
through the middle of next week. An even blend of the ensemble
means yielded solutions that are fairly close to continuity from
yesterday.
Therefore, the WPC forecast grids for Alaska were based on a blend
of the 06Z GFS/12Z GFS & GEFS, the 12Z ECMWF/12Z EC mean, together
with smaller contributions from the 12Z CMC/CMC mean. The blend
is then progressively weighed toward an even blend of the ensemble
means toward the end of the forecast period.
...Weather/Hazard Highlights...
Winds should be subsiding across the Aleutians later next Monday
as a cyclone center is forecast to pass south of the islands.
Thereafter, flow around a Bering Sea frontal wave should increase
precipitation somewhat from the eastern Aleutians to southwestern
mainland Tuesday to Wednesday along with gusty winds. Meanwhile,
generally quiet conditions are expected for much of mainland
Alaska, with occasional snow showers along the North Slope and the
Arctic Coastal Plain. The southern coast and Panhandle should see
a modest increase of rain/snow toward midweek as a broad cyclonic
circulation is forecast to meander over or south of the Gulf of
Alaska.
Expect above normal temperatures to dominate much of interior
Alaska to start the new week. A slow cooling trend is then
anticipated for the entire area as heights aloft are forecast to
slowly decline, leading to progressively colder readings along the
southern periphery of Mainland and into the Alaska Panhandle
toward midweek as the broad cyclonic circulation over the Gulf
edges closer toward the coast.
Kong
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
Hazards:
- No significant hazards are expected over Alaska during this
forecast period.
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