Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
227 PM EDT Mon Aug 05 2019
Valid 12Z Fri Aug 09 2019 - 12Z Tue Aug 13 2019
...Guidance/Predictability Assessment and Weather/Threats
Highlights...
Models and ensembles continue to depict an overall blocky medium
range flow pattern over Alaska and vicinity anchored by an
amplified ridge extending from the eastern Bering Sea and Alaskan
west coast down through the Alaksan Peninsula and far southwestern
Gulf of Alaska. Guidance is generally well clustered into Friday
when 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 remains on track to lift into the Bering Strait by Fri
on the western periphery of the main ridge. Organized
precipitation through the Bering Sea weakens into the western
Alaska mean ridge position aloft. More amplified upper trough
development is still expected to reach the western Bering Sea by
next weekend with deep 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 with surface frontal surges as 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
No significant hazards are expected over Alaska during this
forecast period.
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