Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 515 PM EST Wed Dec 02 2020 Valid 12Z Sun Dec 06 2020 - 12Z Thu Dec 10 2020 ...Major Gulf of Alaska Storm offers a heavy precipitation and high wind threat for southern to southeast Alaska this weekend and early next week.... ...Guidance and Uncertainty Assessment... Guidance variance has decreased overall, bolstering forecast confidence in the formation of a major Gulf of Alaska storm this weekend into early next week. The 12 UTC GFS and ECMWF are well clustered models that reasonably continue to trend increasingly deep with the main storm considering favorable upper support to provide a seemingly good forecast starting point Sun/Mon into Tue. Forecast spread increases enough through next midweek to favor a blend of still reasonably compatible 12 UTC GEFS/ECMWF ensemble means. The WPC Alaskan medium range product suite was accordingly derived along with the 19 UTC National Blend of Models. This solution maintains good WPC continuity. ...Weather/Hazards Highlights... A deep and large storm with amplified upper trough/low support has a growing guidance threat signal for major multi-day maritime disruption and heavy precipitation/high winds across the Gulf of Alaska and onshore into southern and southeast Alaska this weekend and early next week. Farther inland to the north, a generally benign weather pattern is expected for much of the North Slope and the Interior except for more modest early next week spillover moisture/snows into the Interior as the aforementioned deep low shifts northward over the Gulf toward southern Alaska. Additional low energies upstream with less certain development potential to monitor are subsequently slated from the northern Pacific toward the Aleutians and vicinity next midweek. Schichtel Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Sat-Mon, Dec 5-Dec 7. - High winds across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Dec 5-Dec 6. 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