Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
243 PM EDT Sun May 12 2019
Valid 12Z Thu May 16 2019 - 12Z Mon May 20 2019
A complicated cacophony of compact closed centers of circulation
will center over the Gulf of Alaska/northeast Pacific late next
week through next weekend. The models/ensembles have devolved into
worse agreement as the forecast has introduced more players in the
otherwise predictable longwave flow, thus favoring the ensemble
means over any single deterministic solution. However, even the
ensemble means again moved away from otherwise good agreement 24
hrs ago with small timing differences increasing with time. The
ECMWF ensemble mean offered the most stability (despite its washed
out appearance) as the GEFS mean again has shown some noticeable
shifts with each cycle (i.e., 00Z --> 06Z). Using the 00Z ECMWF
ensemble mean as a best starting point, the deterministic models
that stayed closer to it and continuity (still a reasonable
solution) were the 00Z ECMWF and UKMET. The recent GFSs (including
the FV3-GFS) were too different in timing to yield a sensible
blend, but their solutions were not necessarily unreasonable. A
blend of just the 00Z ECMWF/ECMWF ensemble mean forged the day 6-8
forecast with low confidence in details. Precipitation will favor
areas along/south of 60N as waves of precipitation rotate
counterclockwise around areas of low pressure that they themselves
will rotate counterclockwise in the Gulf. Interior/northern areas
will remain mostly precipitation-free except around next Fri/Sat
as a weakness aloft passes westward out of Canada.
Fracasso
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