Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
719 PM EDT Tue Jun 15 2021
Valid 12Z Sat Jun 19 2021 - 12Z Wed Jun 23 2021
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of well clustered guidance of the 12 UTC
GFS/ECMWF, and the 12 UTC GEFS/CMC/ECMWF/NAEFS ensemble means Day
4-8 (Saturday-next Wednesday). Guidance forecast spread continues
to indicate above normal predictability. A general model
compromise starting from Day 4 followed by increasing use of the
ensemble means for Days 6-8 should provide a good starting point.
This will allow a mid-latitude cyclone to track near the Aleutians
at a similar speed and intensity as continuity for early to middle
of next week.
...Weather/Threats Highlights...
A lead system that tracks from south of the Alaskan Peninsula
toward the Gulf of Alaska this weekend is expected to produce
unsettled maritime conditions along with a periodic rain focus
into the Alaskan Peninsula and southern to southeast Alaska.
Meanwhile, a warming mean upper ridge is expected to linger over
much of the Interior and North Slope into the weekend, but
embedded small scale impulses may support spotty local activity.
The upper ridge transitions from the weekend into early next week
as the pattern modifies to allow potentially vigorous ocean storms
lifting toward the Aleutians, the Alaska Peninsula, and
Southwest/southern Alaska. This is slated to occur as ample upper
trough/system energies approach from eastern Asia and the Pacific
mid-latitudes to interact with lingering northern stream energies
and entrain deeper moisture. This offers an emerging maritime and
regional threat to monitor as an occluded cyclone will most likely
impact areas from the Aleutians to the Alaskan Peninsula in much
wetter pattern toward the middle of next week.
Kong/Schichtel
Hazards:
No significant hazards are expected over Alaska during this
forecast period.
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