Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
333 PM EDT Sat Aug 03 2019
Valid 12Z Wed Aug 07 2019 - 12Z Sun Aug 11 2019
...Pattern Overview and Guidance/Predictability Assessment...
Medium range models and ensembles show an overall blocky flow
pattern over Alaskan and vicinity anchored by an
amplified/stablizing ridge extending from the eastern Bering Sea
and Western Alaska down through the Alaksan Peninsula and western
Gulf of Alaska. Guidance is generally well clustered into
Wednesday and a composite solution seems reasonable. However,
significant forecast track/emphasis spread with a series of
embedded weather focusing systems working around this feature
becomes especially evident days 5-8. Given uncertainty, a
compatable 12 UTC GEFS mean and 00 UTC ECMWF ensemble mean blend
is preferred over more varied deterministic model gudiance. This
forecast strategy was collaborated with local WFOs.
In this pattern, an amplified upper level trough and surface
low/system is slated for an uncertain lift over the Bering Sea
Wed-Fri on the western ridge periphery. Organized precipitation
through the Bering Sea and Aleutians weakens into western Alaska.
More amplified upper trough development may reach the western
Bering Sea by next weekend with deeper surface low/frontal
genesis, with eastward progression slowed by the resilient
downstream ridge. A series of mid-upper level trough energies to
round the top then dig southeastward to the lee of the ridge over
the interior then Southeast Panhandle. Expect a cool and showery
pattern focused by modest but renewing northeast Gulf of Alaska
surface system developments.
Schichtel
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