Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
651 PM EDT Sat Apr 03 2021
Valid 12Z Wed Apr 07 2021 - 12Z Sun Apr 11 2021
...A cold pattern for Alaska and stormy offshore waters...
...Guidance/Uncertainty Assessment...
Guidance shows an amplified large scale pattern over Alaska at
medium range time scales, generally with a cold trough dug over
the state and a ridge to the west that is gradually worked into by
additional but uncertain upstream trough energies. Significant
embedded system differences become increasingly evident over time.
Accordingly, the WPC Alaskan product suite was primarily derived
from a blend of the 12 UTC GFS/ECMWF, the 12 UTC GEFS/ECMWF
ensemble means and the 19 UTC National Blend of Models, but with
increasing weight applied to the ensembles over time. Manual
adjustments were then applied to the blend to ensure offshore low
system strength and circulation consistent with favorable upper
support, predictability and to account for any weakening due to
the blending process.
...Weather/Hazards Highlights...
An Arctic vortex will dig over an unsettled North Slope and
Interior next week and significantly cool the region.
Digging/phase energies will support recurring
cyclogenesis/frontogenesis over the Gulf of Alaska. This will
favor adverse maritime conditions and some periods of terrain
enhancing precipitation for Southeast Alaska and the Panhandle.
The mainland should dry out as frigid high pressure settles in.
This would allow below normal temperatures to expand across almost
all of Alaska, with the coldest anomalies (as much as 20-30+ below
normal) across the Interior. Upstream system and progression
entering the Bering Sea by later in the week remains quite
uncertain, but should bring unsettled maritime conditions.
Enhanced winds and precipitation will also work across the
Aleutians and may reach the mainland next weekend.
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
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