Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
549 PM EST Sun Jan 19 2020
Valid 12Z Thu Jan 23 2020 - 12Z Mon Jan 27 2020
...Well below average temperatures 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 across the Aleutians and into the Bering
Sea from Thu 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 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 next weekend. This
setup should keep the Aleutians as well as Southeast Alaska with
relatively high precipitation chances due to the active storm
track. Although greater precip chances may work their way north
into southern mainland Alaska by the weekend as the upper low
develops overhead.
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 relatively to
yesterday. Needless to say, that aspect of the forecast remains
quite chaotic with very low predictability. A blend of the
ECWMF/CMC 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
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