Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
658 PM EDT Thu Mar 26 2020
Valid 12Z Mon Mar 30 2020 - 12Z Fri Apr 03 2020
...Below to much below normal temperatures to continue over parts
of Alaska into next week...
An anomalous upper-level high centered across northwest mainland
Alaska early next week will displace arctic air southward to its
east, keeping much of mainland Alaska cold through much of the
week. High temperatures Mon-Wed are forecast to be 10-25 deg F
below average across the southern half of mainland Alaska, as well
as much of Southeast Alaska, with the arctic air mass expected to
reinforce a persistent stationary frontal boundary just offshore.
The North Slope will be the significant exception, where above
normal temperatures are forecast through the medium range.
Ensemble show a general consensus that the upper ridge should
gradually weaken as it shifts eastward through the middle of next
week, eventually breaking down the strong arctic connection and
allowing temperatures across Alaska to slowly warm. Surface high
pressure across mainland Alaska should keep conditions dry for
many areas, while a relatively active storm track across the North
Pacific remains well south of mainland Alaska, with some potential
precipitation for the Aleutians, the Alaska Peninsula, and perhaps
southwestern mainland Alaska. Models/ensembles show some modest
consensus on the idea of a deeper low pressure system moving into
the Bering Sea next Thu-Fri, with a potential pattern change in
the works for Alaska, as the removal of the blocking ridge present
earlier in the week potentially opens Alaska up to somewhat more
progressive westerly mid/upper-level flow (and warming
temperatures)
The WPC forecast was initially based heavily on the 12Z ECMWF,
along with some use of the GEFS/NAEFS ensemble means, during days
4-5 (Mon-Tue). The ECMWF made a significant adjustment from its
previous run, with the 00Z run representing an outlier in terms of
the overall model/ensemble consensus, and the 12Z run falling into
line. During days 6-8 (Wed-Fri), majority forecast weighting was
shifted to the GEFS/NAEFS ensemble means, with some continued use
of the deterministic ECMWF through the end of the forecast period.
Ryan
Hazards:
-High winds across portions of the Alaska Panhandle, mainland
Alaska, and the Aleutians, Sun-Mon, Mar 29-Mar 30.
-Much below normal temperatures across portions of mainland
Alaska, Sun-Wed, Mar 29-Apr 1.
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