Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
702 PM EST Wed Mar 09 2022
Valid 12Z Mon Mar 14 2022 - 12Z Fri Mar 18 2022
...Overview...
A strong shortwave is expected to round the top of the Siberia
upper ridge this weekend and then dive south into the Mainland
early in the week. This will allow a northeast-southwest oriented
upper trough to make its way through the eastern part of the
state; possibly with an embedded upper low reaching the southern
coast/southwestern Mainland by the middle of the week. Farther
south and within fairly active Pacific flow, a strong mid-latitude
system should weaken somewhat as it approaches the Panhandle early
next week. At the same time a trailing system will likely track
just south of the Aleutians, but with some uncertainty over what
interaction may occur between it and initial low pressure/upper
dynamics lingering over the Aleutians. Some details of these
Pacific systems will depend on exactly how the upper trough over
the mainland evolves.
...Guidance/Predictability Assessment...
The latest runs of the models and their respective ensemble means
have continued to favor a deeper trend for the trough that will
move through the Mainland. It was noted yesterday that a majority
of the consensus pulled the upper lower further to the southwest,
leading to the precipitation extending further west across the
southern coast. The 12Z run of the GFS has shifted west of the 06Z
solution and the 12Z ECWMF has also trended a little further west
as well. The 12Z UKMET is fairly clustered with the main features
but is not as deep; whereas the 12Z CMC is deeper, but is tracking
faster/further east than the cluster. The deterministic and the
ensemble means are all showing an upper low around the far
southwest corner of the mainland.
There is still some uncertainty with the track and evolution of
the systems coming from the Pacific, especially for the leading
low that will approach the Southeast.
Regarding Pacific systems, there are still important
track/evolution differences for the leading low tracking toward
the Panhandle early next week. The past couple ECMWF runs have
been on the southern side of the spread at that time but the 12Z
run did at least trend north of its previous run. Remaining
models and means show a somewhat farther north track and/or
northward elongation or redevelopment in response to the
amplifying mainland upper trough. Meanwhile guidance has been
inconsistent with some details of the system tracking south of the
Aleutians, partially due to uncertainty over how much interaction
may occur with residual dynamics/low pressure over or near the
Aleutians. The 12Z ECMWF is somewhat on the northern side of the
spread. By late in the period the ensemble means agree that the
primary focus for low pressure should eventually gravitate to the
northeastern Pacific/Gulf of Alaska due to the mainland upper
trough.
The WPC forecast utilized a multi-model approach in order to
encompass the best placement and amplitude within the cluster of
solutions, beginning with the 06Z/12Z GFS/12Z ECWMF/12Z CMC/12Z
UKMET (lesser weighting of the CMC and UKMET due to more
variability with amplitude and placement) and transitioning to 30
percent of the ensemble means by the end of the forecast period.
The inclusion of the deeper means helped reduce the noise in the
Pacific while trending toward the trough/low near southwest Alaska.
...Weather/Hazard Highlights...
A vast majority of the Mainland will be generally dry over the
course of this forecast period while the precipitation will focus
over the southern coastal areas and across the Southeast.
Initially the precipitation will be light and at time moderately
heavy but as the weekend progresses, the intensity and areal
coverage will lessen. As the low approached the Panhandle by
Monday, precipitation will increase again and expand back along
the southern coast and the adjacent areas inland. Another system
reaching the Northeast Pacific/Gulf of Alaska may enhance
precipitation around Wednesday. Since this time period has more
uncertainty, confidence on the amount coverage and intensity of
the precipitation is about fair/average at this point. The
Aleutians may see periods of mostly light precipitation. There
will likely be brisk to strong northerly winds spreading across
the Bering Sea and Aleutians by Tuesday-Wednesday.
Above normal temperatures will persist this weekend over the
southern Mainland and North Slope while below normal readings
(especially for highs) in-between and over the eastern mainland.
Temperatures will likely trend cooler as the trough settles into
the mainland by early next week, changing to below normal for
mid-March. Some pockets of above normal readings could linger over
the North Slope and for min temperatures in the far south. Expect
most of the Panhandle to see below normal highs through the period
and a mix of above or below normal lows.
Campbell
No significant hazards are expected over Alaska during this
forecast period.
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