Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
800 PM EDT Tue Oct 27 2020
Valid 12Z Sun Nov 01 2020 - 12Z Thu Nov 05 2020
...Guidance/Predictability Assessment...
Model guidance initially is in better good agreement with the
compact low crossing the Aleutians into the Gulf of Alaska.
However spread with the low in the Arctic and the low in the
western Bering is enough to cause downstream phasing with the Low
in the Gulf by the middle of the extended period, and continues
through the end of the period. Even though this is occurring, the
general synoptic pattern is handling well. Chose to maintain
continuity by utilizing the 12Z ECWMF/GFS/CMC early with
increasing amounts of the ensemble means in the later period.
...Weather/Threats Highlights..
A long duration of deep moisture will be directed onshore over
parts of the southern Mainland and the panhandle. Several inches
of rain could fall over the lower elevations with snow possibly
exceeding a foot in the higher terrain through at least Sunday
November 1st. The compact low crossing the southern Aleutians into
the Gulf will have strong wind-driven rains over the region. There
will be a brief lull before another occluded low pressure system
tracks south of the islands. A robust polar low will pass near the
north shore through Saturday afternoon which will likely lead to
some coastal flooding and heavy freezing spray. Colder weather is
expected across the northern and eastern portions of the Interior,
with more sub-zero high temperatures likely by the second half of
the forecast period.
Campbell
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Fri-Sun, Oct 30-Nov 1.
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