Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
610 PM EDT Tue Jun 30 2020
Valid 12Z Sat Jul 04 2020 - 12Z Wed Jul 08 2020
...Guidance/Predictability Assessment...
The latest guidance continues to show a double low/trough over the
Bering Sea with ridging over the North Pacific into the
west-central Mainland through the majority of the extended
forecast. The 12Z ECWMF hinted that the ridge would break down,
allowing shortwave energy to come into the interior- while the
rest of the solution maintained the ridging. This may be an early
signal that the strength of the ridge may weaken by early next
week, however that was the only solution at this time suggesting
that evolution. Therefore to maintain continuity, opted to favor a
slower progression with the low/trough over the Bering
Sea/Aleutians, which would mean a slightly heavier weighting
toward the 12Z GFS and its ensemble mean. Other models included in
the WPC Alaskan medium range product suite for days 4-8 12Z
ECMWF/UKMET/Canadian and NAEFS.
...Overview and Weather/Hazard Highlights...
A weakening system over the Bering Sea will slowly move eastward
across the North Slope and into the Interior. This will usher in
showers with its passage through the region. Meanwhile, with the
blocking-like pattern, the deepened low over the Bering Sea will
make very little progress; which will keep it offshore through the
weekend and into early next week. In turn, this will keep a
protracted maritime wind/wave hazard. A lead weather focusing
front will be slow to shift over the Aleutians toward
western/southwest Alaska and the Alaskan Peninsula. The eastward
motion will be inhibited by a warming mainland upper ridge
building over the extended holiday weekend. The gradual westward
shift of the summer ridge axis more into western and southwest
Alaska into early next week leaves room for temperature moderating
and unsettling upper trough digging from the Arctic and northwest
Canada down through the eastern Interior and Southeast Panhandle.
Campbell/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
Hazards: 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