Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 625 PM EST Mon Dec 21 2020 Valid 12Z Fri Dec 25 2020 - 12Z Tue Dec 29 2020 ...Guidance and Uncertainty Assessment... Overall, the global model ensemble means agree fairly well through the medium range period. A large and intense cyclone is forecast to move across the Aleutians into the Bering Sea during the weekend. This system is well presented by the ensemble means with good consistency. Nevertheless, the deterministic solutions indicate more uncertainties. The 00Z ECMWF solution appears to be most reasonable since it shows good continuity and is most compatible with the 12Z GEFS/00Z EC mean. However, the 12Z ECMWF seems to have difficulties handling the system as it deviates further and further from the ensemble mean solutions with time. For the early part of the period, deterministic solutions suggest that a couple of relatively compact cyclones will likely brush up the southern coasts on Christmas Day--one just off the coast of the Alaska Panhandle, the other one across the Alaska Peninsula. The WPC forecast charts for Alaska were constructed based on a general blend of the 12Z GEFS and 00Z EC mean together with the 06Z and 12Z GFS, the 00Z ECMWF, and some 12Z ECMWF early in the forecast period. More ensemble means were used later in the period. ...Weather/Hazards Highlights... The forecast period should begin with a couple of smaller scale cyclones forecast to bring periods of enhanced precipitation and stronger winds across/near the Alaska Peninsula and Alaska Panhandle on Christmas Day. These cyclones should weaken considerably on Saturday as the next large scale cyclone is forecast to intensify and track toward the Aleutians, where gale to storm force winds and periods of heavy precipitation appear likely through the Christmas holiday weekend. The system should slowly weaken early next week as it spreads moderate precipitation across the Alaska Peninsula. Across mainland Alaska, milder than average temperatures will prevail through the weekend before gradually cooling down to near normal levels for both the northern and southern portions of the state. Kong 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