Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
202 PM EDT Sun Aug 04 2019
Valid 12Z Thu Aug 08 2019 - 12Z Mon Aug 12 2019
...Guidance/Predictability Assessment and Weather/Threats
Highlights...
The latest models and ensembles still show an overall blocky
medium range flow pattern over Alaska and vicinity anchored by an
amplified/stablizing ridge extending from the eastern Bering Sea
and Western Alaska down through the Alaksan Peninsula and far
western Gulf of Alaska. Guidance is generally well clustered into
Thursday and a composite solution seems reasonable. However,
significant forecast track/emphasis spread and run to run
variances with a series of embedded weather focusing systems
working around this feature again become 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. The forecast strategy was, as
always, collaborated with local Alaskan WFOs.
In this pattern, an amplified upper level trough and surface
low/system is slated for an uncertain lift over the Bering Sea
into Thu-Fri on the western periphery of the main ridge. 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 main ridge. Well downstream, 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
reinforcement of 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