Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
617 PM EST Mon Jan 20 2020
Valid 12Z Fri Jan 24 2020 - 12Z Tue Jan 28 2020
...Well below average temperatures expected to return to most of
mainland Alaska by late in the week...
Models/ensembles show good consensus that an upper level ridge
should build northward into the Bering Sea from Fri onward, with a
closed upper high center eventually migrating toward eastern
Russia by early next week. The downstream implication for much of
mainland Alaska will be a strong surface high intensifying near
the Bering Strait and increasingly cold conditions. High and low
temperatures approaching or even exceeding 20 deg F below average
are possible by late week into the weekend, especially across the
Interior, southwestern mainland Alaska, and northern Alaska
Peninsula. Arctic shortwave energy should dive south along the
eastern periphery of the upper ridge, the amplitude of which now
looks sufficient to interact with additional shortwave energy from
an active North Pacific jet, resulting in potential development of
a closed upper low somewhere near southern mainland Alaska or
perhaps in the Gulf of Alaska by late this week. This setup should
keep the Aleutians as well as Southeast Alaska with relatively
high precipitation chances due to the active storm track. Although
greater chances for snow may work their way north into southern
mainland Alaska by the weekend as the upper low develops.
Models continue to struggle with the evolution and progression of
low pressure systems crossing the North Pacific and the Gulf of
Alaska during the extended period, although somewhat better
clustering was evident among ensemble members today compared to
recent days. Needless to say, that aspect of the forecast remains
quite chaotic with below average predictability. A blend of the
ECWMF along with the ECENS/GEFS ensemble means was used throughout
the extended forecast period. More weight was placed on the ECMWF
relative to other guidance early in the forecast period, with a
gradual shift to heavier weight place on ensemble means through
time.
Ryan
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
- Much below normal temperatures across portions of mainland
Alaska, Fri-Mon, Jan 24-Jan 27.
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