Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
653 PM EST Wed Mar 3 2021
Valid 12Z Sun Mar 7 2021 - 12Z Thu Mar 11 2021
...Overview and Guidance/Uncertainty Assessment...
The medium range period begins on Sunday with a broad upper level
ridge axis over western Alaska and upper level lows over the
southern Gulf of Alaska and eastern Siberia. By next Tuesday, a
narrow ridge axis will likely exist over eastern mainland Alaska
and the Yukon Territory, while the upper level gyre remains in
place over eastern Siberia. There is still a chance for an
organized Pacific storm system to affect the Aleutians and perhaps
southwestern mainland Alaska by the middle of next week
The 12Z deterministic model guidance is in good overall synoptic
scale agreement over the Alaska domain through the upcoming
weekend. Differences emerge with the GFS and the GEFS mean early
next week with more broad upper ridging just south of the
Aleutians, whereas the CMC, ECMWF, and the GFS parallel are
portraying less of a ridge. For the storm system next week, the
degree of uncertainty has actually increased compared to
yesterday, with the ECMWF much weaker with today's run, and major
latitudinal differences between the CMC and GFS. Given the
decrease in forecast confidence for the second half of the
forecast period, more of the EC mean was incorporated compared to
yesterday's forecast to account for the uncertainty.
...Weather/Hazards Highlights...
Several rounds of light to moderate snow appear 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 if the storm system next week over the Aleutians
comes to pass. 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:
- Heavy precipitation across portions of mainland Alaska and the
Alaskan Peninsula, 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