Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 553 PM EST Tue Feb 25 2020 Valid 12Z Sat Feb 29 2020 - 12Z Wed Mar 04 2020 ...Major Weekend Aleutians/Bering Sea Storm and Cold Interior Temperatures... ...Guidance/Predictability Assessment and Weather Highlights/Threats... An upper-level high across eastern Siberia will allow for renewed influence from Arctic shortwave energy down across much of mainland Alaska, with another round of very cold temperatures likely. Farther south, models and ensembles strongly agree that a very active North Pacific storm track will offer strong potential for a deep storm to cross the Aleutians to the southern Bering Sea this weekend. This will bring a major threat of hostile maritime conditions, with high winds and heavy precipitation increasingly working to the Aleutians and the Alaska Peninsula/Southwest Alaska. This will be supported by a long fetch moisture plume. The 12 UTC GFS/ECMWF solutions seem well in line with ensembles and WPC continuity. Downstream energy transfer may then support organzied triple point low development over the northern Gulf of Alaska through early next week. Stretching flow may support spread of moderate to terrain enhanced heavy precipitation into southern/southeast Alaska. This seems quite reasonable even though forecast spread and uncertainty increases significantly next week. Meanwhile, there is now less guidance signal for a second deep low to approach the Aleutians next Tuesday, but WPC progs still show an organized low given potential upper support. A blend of the reasonably consistent and compatable GEFS/ECMWF ensemble means was coordinated with local WFOs to use for these longer time frames amid growing model variance. Schichtel 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 Hazards: - High winds for parts of mainland Alaska and Aleutians, Fri-Sun, Feb 28-Mar 1. - Much below normal temps for parts of mainland Alaska, Fri-Tue, Feb 28-Mar 3. - High significant wave heights for the coastal Aleutians, Sat-Sun, Feb 29-Mar 1. 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