Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
531 PM EST Sat Dec 14 2019
Valid 12Z Wed Dec 18 2019 - 12Z Sun Dec 22 2019
A blend of the ECMWF/UKMET/CMC was preferred as a forecast
starting point during days 4-5 (Wed-Thu). These solutions were
relatively agreeable with respect to low pressure moving east
across the Gulf of Alaska, while the GFS was on the
western/southern fringe of the spread. Farther west, model
consensus has improved with respect to a relatively deep low
entering the western Bering Sea on day 5, and the aforementioned
blend should resolve this system favorably. Farther north, upper
ridging across the arctic is forecast to migrate toward Siberia
during the early extended period, allowing arctic shortwave energy
to carve out lower heights across the North Slope and the
Interior, with most solutions showing an upper low developing
across the North Slope by Fri. Also by days 6-8 (Fri-Sun),
deterministic solutions show another wave of low pressure
developing along an active North Pacific frontal zone, perhaps
nearing the Aleutians by Sun. While models agree on the potential
for this system, solutions vary widely on the track, timing, and
intensity (although a number of solutions suggest the potential
for a deep system). Given increased spread during days 6-8, went
more heavily toward ECENS/NAEFS ensemble means during that time
frame.
This pattern should initially favor wet conditions across southern
mainland Alaska very early in the extended period, the axis of
best moisture should shift east into the Panhandle/Southeast
Alaska from the middle of next week onward. Farther north,
initially above average temperatures across much of the Interior
will be replaced by below average temperatures as upper heights
fall by early next week. Dry conditions should prevail across most
of the Interior, however.
Ryan
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards
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