Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
625 PM EST Tue Nov 26 2019
Valid 12Z Sat Nov 30 2019 - 12Z Wed Dec 04 2019
Upper troughing will slowly migrate out of the western Bering Sea
this weekend into mainland Alaska, with a ridging building into
the Bering behind it. The models/ensembles continue to shift with
embedded system timing/track/depth, but overall have maintained
good synoptic agreement. Overall, the 12Z ECMWF represented the
best deterministic solution near its 00Z ensemble mean, followed
by the UKMET/Canadian in most places and also the 12Z GFS. Trended
much more toward the ensemble means, in particular the ECMWF
ensemble mean, by next week as incoming systems showed less
predictability on the back side of the upper low.
System of interest will approach the AKPEN early Sunday then cross
ENS over Kodiak into Prince William Sound per the forecast. The
GFS lied to the east while the UKMET was to the west (Canadian
well to the northwest), leaving the 12Z ECMWF in the middle near
its ensemble mean. Though the GEFS mean was farther northwest as
well, opted to stay closer to continuity which seemed to be near
the broad mid-point. This should bring a period of modest to
locally heavy coastal rain and inland/mountain snow from the Kenai
eastward to the Panhandle Mon-Tue before exiting by Wednesday.
To the north, GFS/GEFS continued to show a folded upper ridge atop
the Bering upper low while the other guidance kept a NW-SE upper
ridge axis (and weak closed upper high) north of Utqiagvik. GFS
may be trending a bit toward the others so it was not necessarily
implausible. Regardless, all models show this feature slipping
westward into the East Siberian Sea as lower heights encroach on
the west coast of Alaska.
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
Hazard:
- Heavy precipitation across portions of mainland Alaska, Fri, Nov
29.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Mon-Tue, Dec 2-Dec 3.
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