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