Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 600 PM EST Sun Dec 19 2021 Valid 12Z Thu Dec 23 2021 - 12Z Mon Dec 27 2021 ...Overview... The extended range over Alaska (Thursday-Monday) will 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. Episodes of light to moderate snow are expected across portions of the mainland. ...Overview and Guidance Evaluation... The latest models and ensembles continue to show excellent agreement on the large scale blocky pattern holding strong through at least next weekend. The main model uncertainties arise from various shortwaves attempting to round the top of the ridge into northern Alaska. There are indications a shortwave may try to erode the northern part of the ridge some late in the period but plenty of differences with regards to timing and strength. Todays WPC forecast used a blend of the deterministic guidance for days 4-5, increasing the ensemble means by the last half of the forecast period to help mitigate these smaller scale differences which may still take several days to resolve fully. ...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 front attempting to cross the island chain. Below normal temperatures across the eastern portion (especially the Northeast) of Alaska should moderate somewhat through the weekend except across parts of the Panhandle which could be 20 to 30+ degrees below normal. Santorelli 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