Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
700 PM EST Wed Dec 23 2020
Valid 12Z Mon Dec 28 2020 - 12Z Fri Jan 01 2021
...Overview and Guidance/Uncertainty Assessment...
Upper pattern will feature ridging from NW Canada atop troughing
that will elongate across the North Pacific. A lead deep system
(940s mb) will slowly dissipate in the Bering Sea early next week.
The 12Z ECMWF/UKMET/Canadian have shifted southeastward with the
parent low placement by 12Z Sun, though the 12Z GFS was a bit
farther WNW closer to the ensemble means. Preferred the ECMWF-led
consensus but with reservation as sometimes the deterministic
models can lead the ensembles, but it's not a guarantee even at
four days out. As the system unfolds to the east, blend of the
guidance acted to tone down any one model solution which was the
preference given the shorter-term uncertainty. This included the
rather robust 12Z ECMWF. Phased out the Canadian as the GFS came
back into better ECMWF/ensemble agreement by the end of the period
across the North Pacific with another system, but trended nearly
fully to the ensemble means by next Thu with low confidence in
details and modest confidence at best in system placement. Upper
low over the far western Pacific next Thu suggests low confidence
in split flow to its east along the Dateline.
...Weather/Hazards Highlights...
Deep system will bring windy conditions to the Aleutians/Bering
and increased precipitation to the AKPen into southern coastal
areas. Southeastern-facing areas of the Kenai peninsula may see
several inches of precipitation in sustained onshore flow, perhaps
aided by triple point or sfc wave development around next Mon.
Less precipitation is forecast for the Panhandle as upper ridging
maintains its presence. Temperatures will generally be near to
above normal through the period.
Fracasso
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:
No significant hazards are expected over Alaska during this
forecast period.
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