Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
540 PM EST Thu Dec 05 2019
Valid 12Z Mon Dec 09 2019 - 12Z Fri Dec 13 2019
...Heavy precipitation expected across southern mainland Alaska...
Multi-low pattern will be present over the high latitudes to start
the week next week before settling into a deeper, singular system
in the Gulf next Wednesday. Models and ensembles were in decent
agreement with a few exceptions for the first few days of the
forecast. The 12Z Canadian was most displaced from the otherwise
good clustering of the 12Z GFS/ECMWF/UKMET for the lead low moving
through Bristol Bay and its attendant cold front to the
south-southeast (providing the moisture pathway from the
mid-latitudes and subtropics for significant rain/snow next
Sun-Tue). Areal extent may be focused, but ensembles suggest
precipitable water anomalies in the +2 to +2.5 sigma range and QPF
over 5" along southeastern Kenai and on the west side of Cook
Inlet.
To the southwest, a pair of systems south of the Aleutians will
morph into a more coherent system by late Tue into Wed. Ridging to
the northeast will hold tight through the end of the week,
allowing/forcing the Gulf parent low to linger and slowly
dissipate as its front pushes past the Panhandle. Trended toward
the ensembles with some details added from the GFS/ECMWF as they
tracked the low in opposite directions with the ensembles in
between. Next system will enter the western Bering late in the
week.
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 southern Alaska, Sun-Tue,
Dec 8-Dec 10.
- High significant wave heights for coastal portions of mainland
Alaska, Sun, Dec 8.
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