Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
649 PM EST Wed Jan 8 2020
Valid 12Z Sun Jan 12 2020 - 12Z Thu Jan 16 2020
...Guidance/Predictability Assessment...
The latest runs of the 12z deterministic guidance show fairly good
agreement on a weakening surface low crossing the northern Bering
Sea on Sunday, with the GFS and GEFS indicating a more northward
track. Farther south, a frontal wave will likely develop into the
next well defined surface low as it enters the southern Gulf of
Alaska by Tuesday and into Wednesday. Both the 12z GEFS and EC
means are indicating a more northern solution with the Gulf low,
whereas the deterministic GFS, ECMWF, and CMC suggest a track
farther south near 45 degrees north. Given the strength of the
upper level high over the Aleutians and western Alaska, the more
southern track appears the most realistic. With the upper level
ridge axis beginning to break down some over the central Aleutians
by mid-week, the next potentially significant surface low may
begin affecting the western Aleutians and the Bering Sea by late
Wednesday or early Thursday, with the 12z GFS and ECMWF among the
fastest solutions. In terms of the WPC forecast over this domain,
a more deterministic blend of the 12z ECMWF, 6z/12z GFS, and CMC
was incorporated through Monday night, and then gradually
increased use of the ensemble means towards the end of the
forecast period.
...Weather/Hazards Highlights...
A building upper ridge over the North Slope and much of the
Interior will partially abate the current spell of frigid weather,
with lingering much below normal temperatures expected early in
the forecast period over the eastern Interior/Southeast and
Panhandle region as post-frontal arctic high pressure continues to
build in from Canada. Temperatures across some of the more
sheltered valleys in the eastern Interior may approach 50 below!
Snow showers and gusty winds are likely for western Alaska on
Sunday as the Bering Sea surface low lifts northeastward. The
shortwave moving into an already unsettled Gulf of Alaska early
next week should bring more modest effects for maritime interests
and perhaps for coastal areas of southern Alaska. The next
surface low for the Aleutians may bring a period of gusty winds
and heavy precipitation by the middle of next week, with
noteworthy differences in timing remaining.
Hamrick
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, Sat-Sun, Jan 11-Jan 12.
- Much below normal temperatures across portions of the Alaska
Panhandle, Sat-Tue, Jan 11-Jan 14.
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