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