Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EST Tue Mar 02 2021
Valid 12Z Sat Mar 06 2021 - 12Z Wed Mar 10 2021
...Overview and Guidance/Uncertainty Assessment...
The medium range period begins on Saturday with a broad upper
level ridge axis over the Aleutians and upper level lows over the
Gulf of Alaska and eastern Siberia. By next Monday, a narrow
ridge axis will likely exist over eastern mainland Alaska while
the upper level gyre develops further over the western Bering.
There is a good chance for a rather strong Pacific storm system to
affect the Aleutians and perhaps southwestern mainland Alaska by
the end of the forecast period.
The 12Z deterministic model guidance is in good overall synoptic
scale agreement over the Alaska domain through the upcoming
weekend, with the CMC displaced westward some with the upper ridge
axis that leads to greater differences with this model run later
in the forecast period. Regarding the timing of the big storm
system next week, the operational GFS is slightly faster than the
ECMWF. It is interesting to note that the GFS parallel is slower
than the relatively well clustered CMC/ECMWF/GFS, and thus not
favored. Given the well defined signal in the GFS and ECMWF for
this system, there was a higher than usual contribution from these
models for days 7 and 8.
...Weather/Hazards Highlights...
Several rounds of light to moderate snow appears increasingly
likely across portions of western/northwestern Alaska and the
Interior in active mid-upper level flow. Stronger pressure
gradients will result in some maritime threats and potential for
high winds for coastal areas, especially with the strong storm
expected next week. Meanwhile, shortwave energy extending down
over the Bering and Aleutians are expected to break eastward
across an unsettled Gulf of Alaska. This will support surface low
developments over the Gulf with the potential for enhanced
precipitation onshore, mainly from the Kenai Peninsula to the
southeast Panhandle region.
Hamrick
Hazards:
- High winds across portions of the Aleutians, Fri, Mar 5.
- Heavy precipitation across portions of mainland Alaska, Fri-Sat,
Mar 5-Mar 6, and Mon-Tue, Mar 8-Mar 9.
- High winds across portions of mainland Alaska, Sun-Mon, Mar
7-Mar 8.
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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