Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
655 PM EST Mon Mar 07 2022
Valid 12Z Fri Mar 11 2022 - 12Z Tue Mar 15 2022
...Overview...
A Siberia upper ridge and its surrounding flow will dominate the
pattern at higher latitudes, with progressive flow across the
mid-latitude Pacific and varying forms of elongated mean troughing
between the two. From late this week into the weekend expect the
upper ridge to extend far enough into the mainland to keep a
modest weakness over far southern/eastern areas. Then consensus
shows a strong shortwave rounding the ridge during the weekend and
dropping into the mainland early next week--ultimately leading to
a northeast-southwest trough by next Tuesday. This feature may
contain an upper low for at least a part of the period. Meanwhile
low pressure near the Aleutians/Alaska Peninsula late this week
should weaken thereafter, followed by a mid-latitude storm that
may track close to the Panhandle by next Tuesday and an upstream
system that tracks a little south of the Aleutians.
...Guidance/Predictability Assessment...
Latest models and means provide reasonable similarity for the
large scale pattern evolution but with some typical uncertainties
for the details. Comparisons supported starting the forecast with
a 12Z operational model blend (somewhat more ECMWF and GFS
relative to the UKMET and CMC, all in order from most to least
weight) which eventually transitioned to half models/half means by
next Tuesday. During the latter half of the period the ECMWF
component consisted of both 12Z and prior 00Z runs.
Guidance generally shows at least a couple areas of low pressure
over the Aleutians/southern Bering Sea into the Alaska Peninsula
early in the period, including a front that extends into the Gulf
of Alaska as of early Friday. These lows should weaken with time.
There is also a hint of weak waviness that could reach the
northeastern Pacific, but most likely missing the Panhandle either
by dissipating or tracking to the south. The favored model blend
in this time frame reflected the most common elements of the
forecast while downplaying features with the least confidence.
For the pattern over the mainland and vicinity during the first
part of next week, the best consensus shows a strong shortwave
(with possible embedded upper low) dropping into the area from the
north to yield a northeast-southwest trough by next Tuesday.
Recent ensemble means have depicted such a trough but in modest
fashion. Operational model runs have varied more significantly,
though latest solutions offer a deeper trough than the means and
still the potential for an upper low. Prior variability made the
model/mean approach a reasonable starting point, trending deeper
than continuity for the trough but not to the degree of the
operational runs yet. The new 12Z ECMWF mean came in noticeably
deeper than past runs.
Finally, there is a general clustering of models/ensembles for a
potentially strong mid-latitude Pacific storm that should weaken
somewhat by the time it approaches the Panhandle next Tuesday
while another system likely tracks just south of the Aleutians.
Details of mainland troughing may begin to have some influence on
this latter system by next Tuesday.
...Weather/Hazard Highlights...
The southern coast and Panhandle may see some light to moderate
precipitation late this week with a frontal system but expect this
activity to trend lighter during the weekend. Lighter and more
scattered precipitation may extend a little farther north into
southern parts of the mainland. Portions of the Panhandle may see
another episode of precipitation early next week with the
mid-latitude Pacific system that eventually tracks toward the
region. The Aleutians may see a period of increased
precipitation/winds around late weekend and early next week with a
system passing by to the south. Precise effects on the Aleutians
will be very sensitive to storm track, and typical guidance error
6-7 days out in time keeps confidence low in defining specifics at
this time.
Expect above to well above normal temperatures over a majority of
the mainland from late this week into the weekend, with the
primary exception being some moderately below normal readings in
eastern and central interior areas. Upper troughing forecast to
settle over the mainland next week should promote a cooling trend,
with increasing coverage of below normal temperatures and
especially for daytime highs. The Panhandle will likely see below
normal highs for most of the period and a mix of above/below
normal lows.
Rausch
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