Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
634 PM EST Fri Mar 05 2021
Valid 12Z Tue Mar 09 2021 - 12Z Sat Mar 13 2021
...Overview and Guidance/Uncertainty Assessment...
An upper low over the East Siberian Sea will drift northward
toward the Pole with quasi-zonal flow underneath it across the
North Pacific/Aleutians. The flow has potential to become
unstable, leading to wave-breaking and a closed low (or two)
across the mid-latitudes, but should otherwise remain mostly
west-to-east along 50N. Consensus has mostly stayed the course on
timing and system track, with perhaps only a slightly slower
progression overall though this could be mired in differing
northern vs southern stream (high latitude vs mid-latitude)
speeds. The 12Z GFS and ECMWF were comparable enough with the
ensemble means though the GFS/GEFS were generally a bit quicker
than the ECMWF and its ensembles. The parallel GFS was slower than
the GFS and showed a lagging upper low to the south, so favored a
slightly slower position than a straight consensus. This would
affect the system headed toward the Panhandle later next week and
how it evolves.
...Weather/Hazards Highlights...
Light to perhaps modest rain/snow is expected with the first
system across the Gulf Tue-Wed after it splits into at least two
pieces (the first well north into the Arctic). High pressure will
settle into the Interior and Southcentral Thu-Sat with colder
temperatures 10-15 degrees below normal. Pacific system will bring
in more organized rain/snow to the Panhandle later next week,
though timing is uncertain as it will depend on system evolution.
Next system in the Bering will bring windy conditions and some
rain/snow to the islands as the parent low stays well northwest.
Fracasso
Hazards:
- Heavy precipitation across portions of mainland Alaska, Mon, Mar
8.
- Heavy snow across portions of mainland Alaska, Mon, Mar 8.
- High winds across portions of mainland Alaska, Mon-Tue, Mar
8-Mar 9.
- High winds across portions of the Aleutians, Thu-Fri, Mar 11-Mar
12.
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