Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
609 PM EDT Fri May 22 2020
Valid 12Z Tue May 26 2020 - 12Z Sat May 30 2020
...Overview and Weather Hazards/Threats...
It remains the case that a blocky large scale flow pattern over
Alaska is expected to stay relatively unchanged next week. An
amplified upper-level ridge is forecast to persist from the Arctic
Ocean across eastern Alaska and into northwest Canada. This will
result in above average temperatures with anomalies upwards of +15
deg F over northern Alaska. This will enhance snow/ice melt, so
please refer to your local office for all seasonal river ice flow
issues.
An upper low and surface system will gradually weaken while
lifting northward on the western periphery of the upper ridge from
the Bering Sea Monday to the Arctic Ocean by Thursday. This system
offers some lingering wind/rain threat and an open water maritime
hazard. A second system will meanwhile organize well south of the
state over the eastern Pacific early next week. Yesterday, this
system was slated to lift slowly northward into the Gulf of Alaska
mid-later next week. However, latest model and ensemble guidance
has strongly trended to suppress system lift and development. WPC
progs now depict a much weaker/uncertain Gulf of Alaska low in
consideration of both continuity and guidance trends. This
solution was collaborated with local Alaskan offices.
...Guidance/Predictability Assessment...
Larger scale predictability across Alaska is above average due to
a relatively stable and blocky flow regime. A composite guidance
solution seems reasonable days 4/5 (Tuesday/Wednesday) and WPC
continuity is well maintained during this period. However, day 6-8
forecast spread is still quite evident with ridge evolution
specifics and especially with the development/track of the second
system. Accordingly, the WPC Alaskan medium range product suite
was primarily derived from a blend of the GEFS/ECMWF ensemble
means along with the 19 UTC National Blend of Models for days 6-8.
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:
- Heavy precipitation across portions of mainland Alaska, Mon, May
25.
- Much above normal temperatures across portions of mainland
Alaska, Mon-Thu, May 25-May 28.
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