Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
518 PM EST Thu Dec 24 2020
Valid 12Z Mon Dec 28 2020 - 12Z Fri Jan 01 2021
...Overview and Guidance/Uncertainty Assessment...
Upper troughing in the Bering will translate ESE into the southern
Gulf/Northeast Pacific later next week as ridging holds over the
Interior/eastern Alaska. After the lead front associated with the
deep Bering upper low moves into the Gulf and weakens Tuesday,
subsequent systems around the upper low's circulation will skirt
along 50-55N. Wavy zonal flow will yield fast-moving and
hard-to-time systems Tue-Thu across the North Pacific. Broad blend
of solutions offered good continuity from the forecast 24 hrs ago,
so no one model was favored explicitly. The GFS appeared a bit
suspect over higher latitudes (Beaufort Sea/Arctic Ocean) with its
upper pattern but otherwise was plausible. By next Tue-Thu,
favored the ensemble means as a best guide with more weight toward
the better-defined 00Z ECMWF ensemble mean vs the 12Z GEFS mean,
though both were fairly close on track/timing considering the lead
time. With a deepening upper low over eastern Asia later next
week, a well-defined system may emerge into the western Bering
with another downstream making the turn northeastward into the
Gulf. A more amplified pattern suggest better predictability going
forward.
...Weather/Hazards Highlights...
Modest to locally heavy rain/snow is possible over
southeastern-facing areas of southern coastal Alaska, especially
the Kenai Peninsula, as the occlusion and triple point low push
through early in the week. Generally lighter and scattered
rain/snow is forecast for Tue-Thu with the systems offshore. By
the end of next week, more organized rain/snow will push through
the Aleutians and perhaps approach the Panhandle. Temperatures
will generally be near to above normal through the period,
especially over western areas of the mainland.
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:
- Heavy precipitation across portions of mainland Alaska, Mon-Tue,
Dec 28-Dec 29.
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