Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
611 PM EDT Sun Apr 04 2021
Valid 12Z Thu Apr 08 2021 - 12Z Mon Apr 12 2021
...A cold pattern for Alaska with maritime storms...
...Guidance/Uncertainty Assessment...
Models and ensembles show an amplified large scale pattern into
medium range time scales, generally with a cold trough dug over
Alaska from the high Arctic and a ridge to the west that is
eventually worked into by ample but uncertain trough energies.
Differences become increasingly significant over time, but recent
runs of the ECMWF/Canadian seem better aligned with ensembles than
the GFS. This is evident with both the high Arctic intrusion this
week and with system and flow transition/progression from the
Bering Sea/Aleutians to the mainland next weekend. Accordingly,
the WPC Alaskan product suite was primarily derived from a blend
of the 12 UTC ECMWF/Canadian, the 12 UTC GEFS/ECMWF ensemble means
and the 19 UTC National Blend of Models.
...Weather/Hazards Highlights...
High Arctic troughing will dig over an unsettled North Slope and
Interior this week and significantly cool the state.
Digging/phasing 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 will 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. Systems entering the Bering Sea later
week and next weekend are less certain, but will bring unsettled
maritime conditions. Enhanced winds and precipitation will also
progress across the Aleutians and are expected to work in earnest
into 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