Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
557 PM EST Tue Feb 04 2020
Valid 12Z Sat Feb 08 2020 - 12Z Wed Feb 12 2020
Models/ensembles show general consensus that an upper-level ridge
axis across the North Pacific will gradually build northward
across Alaska through the extended forecast period. The dominant
storm track will initially be across the eastern Aleutians and
north into the eastern Bering Sea, but with the ridge building
this storm track should gradually shift westward into next week -
closer to the Date Line by next week. The 12Z ECMWF/GFS showed
relatively good consensus through the first half of the forecast
period, with a surface low moving into western mainland Alaska on
Sat, and another quickly following it late Sun - each of these
producing potentially strong/high winds near the coast, and
precipitation spreading as far north as the Interior. Farther
east, another relatively weak wave of low pressure should move
along a lingering frontal boundary in the Gulf of Alaska Sun
night-Mon, bringing a round of precip to the Panhandle/Southeast
Alaska. After that - the storm track shifts west, with most
guidance showing a relatively deep low pressure system crossing
the western Aleutians/Bering Sea Mon night-Wed (potentially a
couple waves of low pressure, although the finer scale details
remain difficult to resolve given the time range). Strong warm
advection ahead of this system should spread additional
precipitation across the Aleutians/Alaska Peninsula and into
portions of western mainland Alaska. Model differences on
track/timing were a bit higher with this system, so increasing
emphasis on ECENS/GEFS ensemble means by that time was used to
help smooth out some of these differences toward a consensus
solution. Given these considerations, a blend of the GFS/ECMWF was
used initially on day 4 (Sat), with a gradual trend toward heavier
weighting of ensemble means each consecutive day, and a majority
ensemble means after day 6 (Mon).
Additionally, with the building upper-level ridge, temperatures
are forecast to warm to near or above average across much of the
state - the North Slope being the significant exception where
colder conditions should linger at least through early next week
before perhaps some moderation by midweek.
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
Hazards:
- High winds across portions of mainland Alaska and the Aleutians,
Fri-Mon, Feb 7-Feb 10.
- Much below normal temperatures across portions of mainland
Alaska, Fri-Sat, Feb 7-Feb 8.
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