Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
556 PM EST Sun Jan 12 2020
Valid 12Z Thu Jan 16 2020 - 12Z Mon Jan 20 2020
...Overview...
Closed high will migrate across the North Slope, through the
Beaufort Sea, and into northwestern Canada near Banks Island late
next week through the weekend. This will allow an upper low near
Haida Gwaii to slip westward underneath the upper high and combine
with westerly flow aloft out of the Bering Sea. Well below normal
temperatures will slowly moderate next week over
eastern/southeastern portions of the state. Precipitation will be
below average outside the western Aleutians with a suppressed
storm track until the end of the period.
...Guidance/Predictability Assessment...
The 12Z GFS/ECMWF/Canadian/UKMET offered reasonable clustering
with the 00Z ECMWF ensemble mean and 12Z GEFS mean to start the
period, Thu-Sat, with high pressure retreating through the Yukon.
Differences in the models related to the track and shape of the
upper high as it morphs east-northeastward. Consensus approach
served well with the latest guidance in good agreement into
Saturday. Thereafter, ensembles show weakening of the upper high
as lower heights take its place across the Gulf/Southcentral.
There, with smaller embedded features, the models continue to
struggle with how to track the shortwaves or weak upper lows.
Trended toward an ensemble blend with a rather amorphous upper
pattern that has lower predictability than the longer wavelength
pattern to the east. System lifting out of the northeast Pacific
may lift toward the Panhandle then perhaps curl back and weaken as
another may fill in behind it next Sun/Mon, based on the forecast
change in the upper pattern.
...Weather/Hazards Highlights...
Much of eastern/southeastern Alaska, especially the Panhandle,
will have lingering much below normal temperatures as arctic high
pressure ~1040mb only slowly retreats into NW Canada. Above normal
temperatures may be limited to the North Slope. Precipitation will
be light late next week given the storm track well to the south,
focused over the Aleutians as a system slides eastward Fri-Sat
south of the island chain. By next weekend, ensembles suggest low
pressure may lift northward just offshore the Panhandle but
uncertain how much precipitation (maybe snow changing to rain) it
may draw northward past about Sitka.
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
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