Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 633 PM EST Mon Dec 20 2021 Valid 12Z Fri Dec 24 2021 - 12Z Tue Dec 28 2021 ...Overview... The extended range over Alaska (Friday-Tuesday) will continue to be dominated by a blocky and anomalously strong upper level ridge and surface high pressure over the northeast Pacific. Multiple shortwaves/storm systems will try to track around the western and northern periphery of the high, but nothing strong enough to break it down significantly through the period. Periods of light snow will be possible across portions of Western Alaska as these systems weaken as they track inland. ...Overview and Guidance Evaluation... The latest models and ensembles continue to show strong consensus on the large scale blocky pattern holding strong into early next week. The main model uncertainties arise from various shortwaves attempting to round the top of the ridge into northern Alaska. There are indications a couple of shortwaves may try to erode the northern part of the ridge some this weekend and again early next week but plenty of differences with regards to timing and strength. Todays WPC forecast used a blend of the 12z GFS and ECMWF with increasing GEFS/ECENS ensemble means through the forecast period to help mitigate the smaller scale differences which may still take several days to resolve fully. The 12z CMC and UKMET both seemed too eager to erode the northern parts of the ridge with a system that drops into northern AK, so those solutions were not included in the blend for today. The resulting final blend solution offers a forecast similar to yesterdays continuity. ...Weather/Hazard Highlights... With strong ridging in place over the Gulf/North Pacific, no areas of heavy precipitation are currently expected over the southern coast and Panhandle region. Some light to moderate snow is possible across mainly western portions of Alaska associated with systems attempting to push inland from the Bering Sea. Areas of light to moderate precipitation are also likely across western portions of the Aleutians ahead of a couple of cold fronts moving across the island chain. A strong pressure gradient setting up along the southern Coast/northern Panhandle region due to a deep surface high in the Pacific and deep surface low off the Northwest U.S. coast may result in the potential for stronger winds near the coast, particularly early in the period. Above normal temperatures initially across western parts of the state should creep farther east through the weekend, with daytime highs as much as 20 degrees above normal for western and North Slope areas. Parts of the Panhandle in contrast could be 20 to 30+ degrees below normal through much of the period. Santorelli Hazards: - High winds across portions of mainland Alaska, Thu-Fri, Dec 23-Dec 24. - Much below normal temperatures across portions of the Alaska Panhandle, Mon, Dec 27. 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