Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
647 PM EST Sun Jan 23 2022
Valid 12Z Thu Jan 27 2022 - 12Z Mon Jan 31 2022
...Overview...
The latest guidance supports the development of an Omega block
pattern setting up over the Alaska region by Thursday with the
amplified ridge axis over the eastern Bering Sea. This would act
to keep storm systems confined to the Gulf/southeast Alaska and
rotating northward across the western Aleutians. Shortwaves may
attempt to temporarily break down the ridge through the period,
but an overall blocky pattern should hold strong into early next
week with possibly a slight eastward shift.
...Guidance/Uncertainty Assessment...
The latest 12z model guidance is in good synoptic scale agreement
on the Omega block pattern over the region through the period,
though plenty of uncertainty in the details. In the Gulf, the GFS
and CMC are displaced farther north than the ECMWF with a surface
and upper low. The low should eventually lift towards the north
and become reinforced through the period by incoming smaller scale
shortwaves/systems. Despite the relatively good large scale
agreement, the smaller scale differences offers low confidence in
the details affecting precipitation across southeast Alaska. To
the west, guidance suggests several deeper surface lows may move
towards the Western Aleutians through the weekend, but again
presents typical uncertainties in placement, strength, and timing.
By early next week, the CMC and ECMWF show a much stronger block
and actually close off an upper high near western Alaska next
Monday (though the CMC is displaced well to the north of the
ECMWF). The GFS continues to support amplified ridging over the
region, but not quite as blocky.
The WPC progs for today over Alaska used a majority blend of the
deterministic GFS, ECMWF, and CMC through day 6. After that,
increased contributions from the ensemble means to help mitigate
the harder to resolve differences at these longer time scales.
This approach keeps the forecast fairly consistent with yesterdays
WPC progs, as well as those downstream across the CONUS.
...Weather/Hazard Highlights...
Arctic High pressure holding strong during the medium range period
will keep much of Mainland Alaska cold and dry. Meanwhile, storm
systems in the Gulf will translate to unsettled conditions along
the Southeast coast and Panhandle regions. Moderate to heavy
precipitation will shift slowly southward through the period with
conditions tending to dry out by early next week as the upper low
moves farther south and some upper ridging tries to build in. The
eastern Aleutians/Peninsula should stay quiet through much of the
period although a couple of storm systems to the west likely
brings renewed wet weather to the western Aleutians, with periods
of gusty winds as well. Temperatures across most of the state
should start out below to much below normal on Thursday (except
the Southeast), though ease with time as the upper ridge axis
shifts slowly inland. By next Sunday-Monday, parts of the Western
Alaska and North Slope regions may see temperatures back to above
normal, with the Panhandle transitioning to much below normal.
Santorelli
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