Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
634 PM EDT Fri Jul 30 2021
Valid 12Z Tue Aug 3 2021 - 12Z Sat Aug 7 2021
...Overview and Guidance/Predictability Evaluation...
Model guidance is in good agreement overall, especially through
Thursday, on the overall synoptic scale pattern across the Alaska
domain. A rather amplified upper level pattern should be in place
with a bit of an omega block setting up. A large upper low over
the Bering Sea and another upper low over the eastern Gulf will be
separated by a narrow upper ridge axis over the Alaska mainland.
The ridge will tend to limit the overall eastward progression of
the Bering Sea low, and this will likely force shortwave
perturbations northward across the Aleutians and the west coast of
mainland Alaska. There will also be a frontal boundary across the
Interior for much of the forecast period with a weakening cold
front along the southern coast. A blend of the 12Z GFS/ECMWF/CMC
was used as a starting point in the forecast process for
fronts/pressures through Thursday, and slightly more of the
EC/GEFS means for Friday and Saturday.
...Weather/Threats Highlights...
Moisture advection surging northward ahead of the Bering Sea
trough/upper low is expected to result in rounds of showers and
perhaps some thunderstorms across portions of western Alaska for
the beginning to middle of next week. A cold front working its
way across the western Mainland by Wednesday should help bring
some moisture into southern Alaska as well. The central and
eastern Aleutians should be the recipients of the heaviest QPF,
with 1 to 2 inches of rainfall possible next week. Moderate to
locally heavy rainfall is also possible across portions of the
Panhandle region as a closed low lingers in the eastern Gulf.
The upper ridge across the Interior should result in temperatures
that are above seasonal averages across much of central and
southern Alaska for the beginning of the forecast period.
Considerably cooler readings are expected across the Brooks Range
and the North Slope where an Arctic surface high will be governing
the weather pattern north of a quasi-stationary front.
Hamrick
Hazards:
- None posted
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