Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
650 PM EDT Fri Jun 12 2020
Valid 12Z Tue Jun 16 2020 - 12Z Sat Jun 20 2020
...Overview and Weather Highlights/Threats...
For the forecast period /Tue-Sat/, the main feature will be the
developing area of low pressure and associated closed upper low
that stalls/slows over portions of the North Pacific, south of the
mainland. An area of low pressure is expected to track from south
of the Aleutians to the North Pacific by mid-week then slow/stall
with a large upper low setting up in the region. This will be
competed by an area of upper ridging over the eastern mainland and
northwest Canada which should persist the above normal
temperatures. Some periods of wet weather could be possible early
in the week with the aforementioned low but widespread hazardous
precipitation is not expected. Across the mainland, the mostly
ridging in place should result in slightly above average
temperatures and mesoscale driven sensible weather characterized
by showers and thunderstorms in the afternoon.
...Guidance/Predictability Assessment...
Forecast confidence ranges from average to slightly above average
for the beginning of the period but quickly drops to below average
by mid to late week as the evolution of a slow moving to
retrograding low pressure south of the Aleutians remains uncertain
the latest forecast guidance. The CMC is the most progressive with
this feature, with a secondary area of low pressure quickly
undercutting it and deepening over the North Pacific. Meanwhile,
the GFS and ECMWF offer somewhat similar solutions, though the GFS
retrogrades the low more than ECMWF. Both models however have
similar timing and depth to the area of low pressure skirting
south of the main low mid week. Finally, toward the end of the
period, another area of low pressure forms well west of the
Aleutians but model agreement is below normal. The ECMWF was most
favored but some components of the GFS were incorporated early on.
From day 6-8, increasing amounts of the ECENS/GEFS were utilized
given the less than favorable model agreement.
Taylor
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