Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
431 PM EST Fri Nov 27 2020
Valid 12Z Tue Dec 01 2020 - 12Z Sat Dec 05 2020
...A pair of North Pacific storms are expected to move into Alaska
Tuesday and Thursday with another large system moving southwest of
the state late next week...
A strong blocking ridge across Saskatchewan will force the flow
across eastern and central Alaska to be southerly through the
period, with low pressure areas impacting the state Tuesday (where
guidance is agreeable) and Thursday (where timing issues are noted
in the guidance). A significant storm is expected to move well to
the southwest of the state late next week. This trio of cyclones
is expected to keep seas across the northeast Pacific unsettled
through the period with wet and windy conditions predominately for
southeast sections of the state. The pressures, 500 hPa heights,
and wind grids were deterministic based (12z Canadian, 12z UKMET,
12z GFS, and 12z ECMWF) from late Monday into Tuesday before
increasing weights of the 12z NAEFS mean and 00z ECMWF ensemble
mean were used thereafter. The remainder of the grids made
greater use of the ensemble means.
Much of the North Slope as well as the eastern two-thirds of the
mainland should see above to well above normal temperatures
through the period within the southerly flow regime with highest
anomalies likely to be for lows (20F or more above normal in some
cases). The Panhandle will tend to be above normal as well except
for some below normal areas that are most likely early in the
week. Expect the best potential for below normal temperatures
over the west/southwest part of the mainland and through the
Peninsula/Aleutians, in an area of persistent mid-level troughing.
Roth
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 the Alaska Panhandle and
mainland Alaska, Mon-Fri, Nov 30-Dec 4.
- High winds across portions of mainland Alaska and the Aleutians,
Mon, Nov 30.
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Mon-Tue, Nov 30-Dec 1.
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