Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
617 PM EST Thu Jan 26 2023
Valid 12Z Mon Jan 30 2023 - 12Z Fri Feb 03 2023
...Much milder than normal temperatures with periods of snow and
mixed precipitation across the southwest/western mainland...
...Model Guidance/Predictability Assessment...
The WPC Alaskan medium range product suite was primarily derived
from a blend of the 12 UTC GFS/ECMWF and GEFS/ECMWF ensemble means
in a pattern with overall near average predictability. A
collaborated forecast plan lead to heaviest blend weighting being
applied to the GFS early next week before switching to the still
compatible GEFS/ECMWF ensemble means for mid-later next week amid
growing forecast spread and uncertainty with embedded systems
despite a reasonably consistent larger scale flow evolution in a
pattern with overall near normal predictability.
...Pattern overview and Weather/Hazard Highlights...
An upper ridge will build over the Gulf of Alaska, the mainland
and Arctic Ocean. The northern portion of the ridge will refocus
as a closed upper high over the Arctic Ocean next week. In this
pattern, shortwave energies and some snow focus will dig to the
lee and underneath into the Interior. Additional system energies
will work inland from the North Pacific/Bering Sea, but also split
across the Gulf of Alaska. Unsettled weather will likely prevail
across the Aleutians, the Alaska Peninsula and into the western
mainland as disturbances blocked by the strong ridge in the
Pacific turn north toward the Aleutians. Periods of precipitation
and gusty winds can be expected for these areas, but the
precipitation is not expected to be excessive as the strong ridge
should weaken the disturbances. Meanwhile, the Panhandle will
remain dry under the ridge axis through the weekend and into early
next week, but the cumulative effects of multiple disturbances
moving across the Pacific will gradually erode the ridge, leading
to an increasing chance of precipitation across the southern
coastline and especially into the Panhandle as next week
progresses.
Above average temperatures will abound especially over the western
mainland under the ridge from the weekend into early next week.
However, there is a growing guidance signal that indicates that
upper troughing may undercut over the Interior as the upper
ridge/high re-focuses over the Arctic Ocean next week. That said,
it generally remains the case for moderate to above normal
temperatures, with possible +30F anomalies for parts of the
northwestern mainland into early next week. Temperatures could
warm above the freezing mark in the southwestern mainland/Bristol
Bay area. There could be impacts from snowmelt with these above
freezing temperatures, and especially if precipitation falls as
rain or freezing rain there due to the relative warmth. This is a
possibility as precipitation crosses the Aleutians/Alaska
Peninsula as well as some possibly gusty winds along a front
stemming from main Bering low, with splitting system enegries
potentially working into the western mainland and also across the
Gulf of Alaska to the Southeast Panhandle.
Schichtel
Hazards:
- Much above normal temperatures across western/southwestern
Alaska, Sun-Tue, Jan 29-Jan 31.
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