Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
614 PM EST Thu Jan 02 2020
Valid 12Z Mon Jan 06 2020 - 12Z Fri Jan 10 2020
Upper ridging is forecast to rebuild over eastern Asia (near the
Amur river or along the Russia/China border) with additional ridge
building in the lower mid-latitudes south of the Gulf of Alaska.
Combined with a weakening upper high in the Beaufort Sea, this
favors a slow erosion of lower heights over the interior amid a
fairly progressive flow out of the North Pacific. The models and
ensembles have struggled with system timing in the quickening flow
but overall aligned adequately.
Relatively larger spread (though nominally smaller compared to
later forecast times) existed at 2-3 days out with lower amplitude
short waves over the North Pacific. This will carry a couple areas
of low pressure toward and into the Panhandle Mon/Tue. The 12Z GFS
favored the trailing low while the 12Z ECMWF/Canadian/UKMET
favored the leading low which was the preferred route (though the
Canadian was notably farther north). Once that system exited into
British Columbia, focus shifted to the Bering Sea. Next system
will likely come in phases, the first of which will be a triple
point low headed toward the Gulf but likely weakening on
Wednesday, then perhaps another front or two rotating under the
old parent low. Ensembles show a good deal of spread with any
system after next Wednesday so opted to carry each along at a
reasonable forward speed. Any of the GFS/ECMWF/Canadian runs was
plausible, but were simply used for just a bit of detail.
Cold temperatures will ease with time as height slowly rise, but
staying below average for early January. Rain/snow will focus
along the Aleutians eastward to the Panhandle but will generally
be light to modest amounts. North of the Alaska Range may be
precipitation-free.
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:
- Much below normal temperatures across portions of mainland
Alaska, Sun-Tue, Jan 5-Jan 7.
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