Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
526 PM EST Tue Jan 12 2021
Valid 12Z Sat Jan 16 2021 - 12Z Wed Jan 20 2021
...Active Gulf of Alaska this weekend into early next week...
...Overview and Guidance/Uncertainty Assessment...
Deep troughing will move out of eastern Asia later this week and
across the northern Pacific this weekend, promoting split flow
across the Dateline. This will drive a couple systems into the
Gulf of Alaska first on Saturday then again on Monday before a
Bering system from the west becomes the focus. The models and
ensembles generally showed this evolution, but differed on timing
of the systems. For the Gulf, the ensemble means were generally
quicker than the 12Z deterministic models, with a slight slower
trend overall. Lead-in pattern into the Gulf will be downstream of
split flow and with ridging over western North America it opens
the door to more meridional flow and generally a slower
progression. However, upstream flow over the western to central
North Pacific will, simultaneously, transition toward increasingly
zonal with a fast 200kt jet off Japan Sunday. Given the slower
deterministic models, opted to put more weight in their cluster of
solutions than the quicker ensemble means. By next week,
transitioned toward increased ensemble weighting for the Bering
system as the models quickly lost any agreement due to the
quickening flow.
...Weather/Hazards Highlights...
The pair of systems in the Gulf will bring several inches of
precipitation to the Kenai Peninsula/southeastern Alaska/Panhandle
with a northeastward push of the fronts. Winds to gale or perhaps
storm force will accompany the areas of low pressure--see the
Ocean Prediction Center for more information. Bering system will
bring in light to moderate precipitation along the Aleutians next
week. Temperatures will be well above average for most areas
during the period owing to ridging nosing into the area from the
southeast.
Fracasso
Hazards:
- High winds across portions of mainland Alaska, Fri, Jan 15.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Fri-Tue, Jan 15-Jan 19.
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