Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Sat Jun 08 2019
Valid 12Z Wed Jun 12 2019 - 12Z Sun Jun 16 2019
An upper low persists during day 4-8 to the north in the Arctic
Ocean with a trough extending south to northern AK. The net
placement among the models/ensembles was southeast of yesterday's
forecasts. Once the stalls around day 6, the consensus was
actually retrogression days 7-8, so the low and attendant
circulation look to be around through the period. The
retrograding low allows upper ridging to extend west from the
Yukon across northern AK by next Sun 16 Jun.
Models/ensembles remain in good agreement overall and a blend of
the 12Z GFS with the 00Z ECMWF/ECMWF ensemble mean/06z GEFS
Mean/00z Canadian global was used, given better than usual
clustering of solutions.
The initial cyclone drifting northeast into the Gulf of AK will
weaken as it moves east day 4 12 June and on day 5 13 Jun as it
approaches the coastal areas of southern to southeast
AK/panhandle. Expect a period of showers for Southeastern Alaska.
The probability of showers declines once the system decays.
The next cyclone drifting slowly east from the Western Pacific
should
move just south of the chain on Wed 12 Jun, bringing rain/windy
conditions through the islands. As the system departs the lower
Aleutians Thu-Fri, the rain and winds subside, while they pick up
closer to the low in Kodiak Island and the southern AK peninsula.
The ECMWF and ECMWF Ensemble Mean move a few hours faster than the
last few GFS and GEFS Mean runs. A blend of the models/ensembles
was used to mitigate the differences.
Next weekend another cyclone originates from a western Pacific
frontal system. Differences grow with time although the 00z ECMWF
and 12z GFS cluster well for now.
Time will tell whether the confluence of solutions remains or not.
I still blended with the GEFS/ECMWF Ensemble means to not commit
to any one track or intensity. Large changes in the new ECMWF with
the cyclone displaced several hundred miles further east next Sun
16 Jun show lower than normal confidence exists.
Petersen
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