Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
615 PM EDT Mon May 10 2021
Valid 12Z Fri May 14 2021 - 12Z Tue May 18 2021
...Guidance/Predictability Assessment...
12 UTC GFS/ECMWF/Canadian model solutions seem fairly well
clustered days 4-7 (Friday-next Monday). A composite blend in
tandem with 19 UTC National Blend of Models guidance seems to
produce a good forecast starting point consistent with a pattern
with above normal predictability while maintaining good WPC
product continuity. Jumped to use the latest ECMWF ensemble mean
by day 8 that offers the best ensemble mean based system
continuity from the day 4-7 model composite despite quickly
growing forecast spread and uncertainty.
...Weather/Threats Highlights...
Ejecting upper trough energies and precipitation focusing surface
lows and associated frontal weather systems will work across the
Gulf of Alaska to southeast Alaska into Friday, undercutting a
warming and stabilizing interior upper ridge. Meanwhile upstream,
amplified/closed upper trough energy is slated to track over the
southern Bering Sea/Aleutians and deepening low pressure will
support increasingly unsettled maritime conditions and inland
feeding enhanced rains and winds across the region with frontal
approach and passage. Activity is expected to translate downstream
into Southwest Alaska, the Alaskan Peninsula, Kodiak Island, the
Gulf of Alaska, the southern interior and then southern and
southeast Alaska through next weekend into early next week with
steady main system progression and lead triple point low
developments and inflow. A second main low with enhanced
rains/winds may meanwhile reach the Aleutians early next week.
Guidance signal for this low is slowly growing, albeit with a less
progressive latest trend.
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