Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 528 PM EST Wed Dec 22 2021 Valid 12Z Sun Dec 26 2021 - 12Z Thu Dec 30 2021 ...Overview... The extended range forecast over Alaska through the middle of next week will continue to be dominated by a persistent and anomalously strong upper level ridge and surface high pressure over the northeast Pacific. Multiple shortwaves/storm systems are expected to track around the western and northern periphery of the high, and the high sinks some to the south by the end of the forecast period. Rounds of light to moderate snow will be possible across portions of the Interior with these systems weaken as they track inland. ...Overview and Guidance Evaluation... The 12Z model guidance suite remains in excellent overall agreement on the dominant upper ridge situated over the North Pacific near 45N/155W through early next week, and then shifting southward by mid-week as a more energetic storm track from eastern Siberia erodes the ridge some. The biggest model differences early on are apparent with the 12Z CMC, which is much faster than the model consensus with the storm system tracking across the central/northern mainland, and these differences continued thereafter, so it was not part of the model blend for this forecast cycle. Elsewhere, the GFS becomes stronger with a trough entering the southwestern mainland by next Wednesday and continues further as it tracks over the northern Gulf region, thus eroding the ridge axis more. Taking these factors into account, a GFS/ECMWF/UKMET blend was used through Monday, and increased use of the ensemble means while retaining some of the GFS/ECMWF along with some previous WPC continuity. ...Weather/Hazard Highlights... A storm system and associated cold front originating from the Bering and western Aleutians is forecast to move quickly across interior sections of the mainland Sunday and weaken by Monday. Moisture advection ahead of the front will support patchy areas of moderate to locally heavy snow across the Seward Peninsula, the southern part of the Brooks Range, and eastward toward the Fairbanks area and the central Interior. Some of this snow will likely be accompanied by strong winds, leading to blowing snow and localized blizzard conditions, particularly in mountain passes. Another round of accumulating snow will be possible by next Tuesday/Wednesday depending on the track of the next storm system entering the Bering. In the temperature department, frigid conditions are expected for eastern and northern portions of the mainland this weekend, with the greatest anomalies expected for inland portions of the southeast Panhandle region. There should be a moderating trend commencing by Monday and a return to above normal readings by the early to middle part of next week for central and western areas. Hamrick Hazards: - Heavy snow across portions of mainland Alaska, Sun, Dec 26. - Heavy snow across portions of mainland Alaska, Tue, Dec 28. - Much below normal temperatures across portions of the Alaska Panhandle, Sat-Tue, Dec 25-Dec 28. 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