Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
659 PM EDT Thu Jul 29 2021
Valid 12Z Mon Aug 02 2021 - 12Z Fri Aug 06 2021
...Overview and Guidance/Predictability Evaluation...
The latest guidance continues to indicate a blocky upper level
ridge building over the mainland Alaska next week which should
keep amplified troughing across the Bering Sea as well as an upper
trough/closed low meandering in the Gulf. The guidance shows good
agreement early on regarding a deep cyclone developing in the
Bering Sea, but plenty of uncertainty thereafter on the details
regarding individual shortwaves rounding the base of the upper low
to send low pressure areas into the Aleutians. Regardless of the
details, the guidance does agree on the large scale that low
pressure will be maintained in some form over the Bering Sea
through next week. Models also show some disagreement on how
quickly the ridge over the Mainland may begin to break down which
could help nudge the Bering Sea (and also low pressure in the
eastern Gulf of Alaska region) just slowly eastward. Given the
uncertainty, the WPC blend trended towards the ECENS and GEFS
ensemble means by the second half of the period. This also
maintains pretty good continuity with the previous forecast.
...Weather/Threats Highlights...
Plenty of moisture streaming northward ahead of the Bering Sea
trough will allow for wet and unsettled weather to continue during
the first half of next week across portions of western and
northern Alaska. Heavy rainfall over the weekend may linger into
Monday, but coverage and amounts should be decreasing by the
beginning of the extended range period with lighter rainfall
lingering into Tuesday and Wednesday. A cold front pushing into
the western Mainland by Wednesday should help bring some moisture
into southern Alaska as well. Moderate to locally heavy rainfall
is also possible across portions of the Panhandle region as a
closed low lingers in the eastern Gulf.
A building upper level ridge should bring temperatures above to
well above normal across much of Alaska early next week. The
exception to this will be across the North Slope region which
should remain on the cold side of a quasi-stationary boundary.
Temperatures elsewhere should begin trending back towards or below
normal by the latter half of the week, dependent on how quickly
the ridge begins to break down and lower heights sneak into the
region.
Santorelli
Hazards:
- Heavy rain across portions of western mainland Alaska, Sun, Aug
1.
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