Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
252 PM EDT Sun May 26 2019
Valid 12Z Thu May 30 2019 - 12Z Mon Jun 03 2019
Deterministic and ensemble model guidance continues to have a good
handle on the overall synoptic evolution over Alaska through the
medium range period. The upper level pattern favors ridging over
mainland Alaska during much of the period which allows for a
meandering main cyclone near the eastern Aleutians which
eventually may retrograde slowly west/south owing to influence
from less predictable shortwaves rounding the base of the trough.
This pattern supports unsettled weather from the Aleutians to the
Panhandle through most of the period, with rounds of locally heavy
precipitation possible along the coast and favored terrain across
the southern Mainland. Across central to northern Alaska, mainly
showery activity and near to above normal temperatures are
expected. Days 4-6 showed very good deterministic model agreement
so a majority 00z ECMWF/12z GFS blend sufficed, with small amounts
of their respective ensemble means. After this, increased the
weighting of the means to mitigate smaller scale differences in
the details, but the agreement was still good enough to include
modest amounts of deterministic guidance. This approach maintains
reasonable continuity with yesterday's WPC Alaska forecast as well
as downstream over the East Pacific/CONUS.
Santorelli
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