Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
348 PM EDT Mon Sep 02 2019
Valid 12Z Fri Sep 06 2019 - 12Z Tue Sep 10 2019
Models showed reasonably good consensus during the first half of
the extended period, and a blend of the GFS and ECMWF served as a
good forecast starting point across Alaska for days 4-5 (Fri-Sat).
This consensus solution resulted in relatively small changes to
continuity. A low pressure system crossing the eastern Aleutians
and moving into the Bering Sea Fri-Sat has shown a slight
northward shift in the model consensus compared to 24 hours ago,
and this trend was reflected in the latest forecast. Models
continue to support the idea of a triple point low developing
across the western Gulf of Alaska by Sun as the system quickly
begins to weaken. This system may produce heavy rainfall across
portions of the Alaska Peninsula and southern mainland Alaska
Fri-Sat.
Shifted to gradually heavier ensemble mean weighting for days 6-8
(Sun-Tue). Model differences begin to increase substantially by
that time frame with another low pressure system crossing the
Aleutians and forecast to move into the eastern Bering Sea. The
forecast for this system was kept relatively close to the ensemble
means. Finally, the GFS brings a very intense low pressure system
into the western Bering Sea by day 8, likely a post-tropical
version of Tropical Storm Lingling (currently across the west
central Pacific). Given very high model/ensemble spread, the GFS
solution was not reflected in the forecast at this time.
Downstream of the active storm track across the Bering/Aleutians,
models show general consensus that an upper-level ridge axis
should remain in place across eastern mainland Alaska through the
extended period.
Ryan
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
- Heavy rain across portions of mainland Alaska, Fri-Sat, Sep
6-Sep 7.
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