Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
641 PM EDT Sun Jun 14 2020
Valid 12Z Thu Jun 18 2020 - 12Z Mon Jun 22 2020
...Overview and Weather Highlights/Threats...
For the forecast period /Thur-Mon/, a closed upper low settles
over portions of the Aleutians and will be the driver for much of
the synoptic pattern for the region through the period. A few
waves of low pressure are forecast to develop along the southern
periphery of this feature, generally tracking well south of the
mainland over the North Pacific. Some periods of unsettled
weather are possible given the upper low in place, 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...
A relatively persistent upper level pattern is expected through
the medium range period characterized by an upper level low
situated over portions of the Aleutians from day 4 (Thursday) to
day 8 (Monday). Several waves of low pressure will ride the
southern periphrey of this main feature in a relative fast
progression, which is where forecast confidence drops below
average. Timing and strength of individual features is difficult
and run to run consistency is average at best. The 12Z CMC, while
offering a decent and agreeable solution for d4, quickly drops out
of favor with significant timing and strength issues compared to
the more stable and reliable ECMWF/ECENS solutions. The 12Z GFS
does show some agreement with the ECMWF through the period at
times, particularly in the latter periods with another area of low
pressure forecast to develop south of the Aleutians. Given the
swings run to run seen in the last couple of days, a more
conservative approach leaned on the ECMWF/ECENS was utilized with
some inclusion of the GFS/GEFS for day 6-8.
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