Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
650 PM EDT Tue Apr 21 2020
Valid 12Z Sat Apr 25 2020 - 12Z Wed Apr 29 2020
...Guidance/Predictability Assessment...
A composite blend of reasonably well clustered guidance from the
12Z ECMWF/GFS produced a good forecast starting point Sat-Sun in a
pattern with average predictability. After Sun, the 12Z GFS does
not seem as well aligned with the ensemble consensus, particularly
with respect to a compact but deep arctic upper low it drops
southward across western Alaska (where other guidance keeps the
energy farther north). Increased the ensemble mean weightings at
longer time frames consistent with growing forecast spread and
uncertainty. This forecast maintains good WPC continuity.
...Weather/Threats Highlights...
A leading low/frontal system along with an enhanced area of
winds/waves/precipitation remains slated for the Gulf of Alaska
into early Saturday, before exiting over the Southeast Panhandle.
Meanwhile upstream, at least two additional emerging frontal
systems with deepening lows and enhanced winds/waves/precipitation
will rotate over the Gulf of Alaska to off Southeast and Southern
Alaska through early next week on the heels of the lead system. By
next Tue-Wed, a deepening low is forecast to enter the western
Bering Sea, with the associated frontal system crossing the
Aleutians with increasing potential for precipitation and winds.
Farther inland over the state, a couple arctic mid-upper level
troughs/impulses will work over the North Slope and the Interior
over the coming week, significantly cooling the recent warm spell.
A few focused areas of snow showers are possible with the passing
mid/upper-level waves, but the air mass will be quite dry, not
supporting much in the way of widespread precipitation.
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:
- Much below normal temperatures across portions of mainland
Alaska, Fri-Sun, Apr 24-Apr 26.
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