Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
612 PM EST Fri Dec 31 2021
Valid 12Z Tue Jan 04 2022 - 12Z Sat Jan 08 2022
...Record cold possible for some areas of the Panhandle next
week...
...Overview...
A blocky pattern will continue through much of the medium range
period over the high latitudes as an upper high over northeastern
Russia meanders in place while changing shape. This favors very
cold high pressure over most of the region south of the Brooks
Range with generally light precipitation confined to immediate
coastal areas of the Aleutians and brisk winds off the continent.
...Guidance Evaluation and Preferences...
Ensembles were in good agreement overall with the lead surge of
vorticity moving westward underneath the expanding upper high from
Southcentral on Monday into the Bering and then northern Pacific
around the start of the period. Upper high is forecast to change
shape from an extended N-S orientation Monday to E-W Tue-Wed
before again elongating N-S Thu-Fri. By then, spread increases and
a general blend/trend toward ensembles was preferred. A
deterministic blend to start sufficed with the good agreement.
Favored the 12Z ECMWF/Canadian a bit more than the GFS as the
former held more high pressure over the Bering while the latter
allowed leftover low pressure to drift across the Aleutians. While
the GFS scenario is plausible, ensembles suggested keeping lower
pressures south of the Aleutians. By the end of the period, a
retraction of the influence of the upper high would allow systems
to approach the southwestern Gulf by next weekend. Transition
toward a more open pattern is usually bumpy regarding
model/ensemble timing/track, so a blend of the ensembles with only
a minority weighting of the deterministic models was used for next
Fri/Sat.
...Weather/Hazard Highlights...
Most of the mainland will see dry weather next week as strong high
pressure over the northeastern mainland on Tuesday settles into
northwestern Canada while a weaker surface ridge likely persists
over the northern half of the mainland into late week. Far
northern/northeastern locations could see a little light snow
toward Thursday or Friday as a weak surface boundary slips through
northwestern Canada. Much below normal temperatures over the
southeastern half or so of the mainland will slowly trend less
extreme with time while readings should stay well below normal
over the Panhandle the entire week with offshore flow.
Temperatures could approach record cold for overnight lows and/or
daytime highs. The North Slope will see a warming trend with
temperatures reaching well above normal by mid-late week before
easing back a bit.
Generally light rain/snow is favored over parts of the Aleutians
into Kodiak Island on easterly flow. A system emerging from the
western Pacific could eventually spread some rain/snow into
Southcentral next weekend as a warm front may push toward or into
the Gulf.
Fracasso
Hazards:
- High winds across portions of the Alaska Panhandle and mainland
Alaska, Mon-Tue, Jan 3-Jan 4.
- High winds across portions of mainland Alaska and the Aleutians,
Sun-Wed, Jan 3-Jan 6.
- Much below normal temperatures across portions of the Alaska
Panhandle and mainland Alaska, Mon-Fri, Jan 3-Jan 7.
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook 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