Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 529 PM EST Mon Dec 12 2022 Valid 12Z Fri Dec 16 2022 - 12Z Tue Dec 20 2022 ...Synoptic Overview... A strong mid-upper level ridge axis is forecast to build northward across much of the western mainland and the eastern Bering going into the weekend, potentially setting up a blocky flow pattern. This ridge may begin breaking down by next Tuesday as a trough from western Canada tries to build into the state. Farther west across the western Bering and far western Aleutians, a building trough will likely support a few surface lows that may affect portions of the Aleutians late in the forecast period. ...Guidance/Predictability Assessment and Preferences... The 12Z model guidance suite has come into better agreement for the end of the week and into the weekend, compared to yesterday's guidance. The latest 12Z CMC is close to the model consensus for Friday, but begins to become considerably stronger with the trough near the British Columbia Coast on Saturday. Later in the forecast period for Sunday through Monday, the GFS/GEFS mean has trended closer to the ECMWF/ECENS solutions in regard to the degree of upper level ridging across the mainland, although the GFS breaks it down sooner. The fronts/pressures forecast was primarily derived from a multi-deterministic blend on Friday, and then mainly using GFS/ECMWF and the ensemble means through next Tuesday. There is still the potential for significant changes early next week given the level of uncertainty with storm systems across the North Pacific. ...Weather/Hazards Highlights... Strong high pressure over the Interior (potentially over 1050mb) is expected to lead to strong radiational cooling and strong surface temperature inversions across many of the inland valleys, with subzero overnight lows likely for the typically colder locations. Off and on showers will likely persist going into the weekend across portions of the Aleutians with generally south or southeast flow continuing. The heavy precipitation associated with the Gulf low on Thursday is expected to abate as the moisture plume crosses the southeast Panhandle region on Friday, with most of the mainland remaining dry during the extended forecast period. Hamrick Hazards: - Heavy snow across portions of southern mainland Alaska, Thu, Dec 15. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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