Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 631 PM EST Sat Dec 19 2020 Valid 12Z Wed Dec 23 2020 - 12Z Sun Dec 27 2020 ...Guidance and Uncertainty Assessment... Model ensemble guidance today shows very good agreement on the overall synoptic evolution relevant to Alaska for the medium range period. A cyclone that is forecast to impact southwestern and southern Alaska with high winds and heavy precipitation near the coast should begin to weaken by next Wednesday. Remnant upper troughing will then extend southeastward into late next week across the Gulf of Alaska, as upper ridging over western Canada gradually shifts eastward. There are decent model signals that a couple of weaker cyclones will edge closer towards the Alaska Panhandle during the Christmas holiday but uncertainty regarding their speeds of motion and intensities remain high. By next weekend, global model ensemble means continue to show decent agreement that the next large-scale cyclone will be moving into the Aleutians. The WPC Alaskan medium-range charts and grid package were based on an even blend of the 06Z/12Z GFS, the 12Z GEFS, the 12Z ECMWF, and the 00Z EC mean, with more weights given to the ensemble means from day 7 to 8. ...Weather/Hazards Highlights... High winds and heavy precipitation near the coast across southwestern and southern Alaska should become less intense by next Wednesday as the attendant large-scale cyclone begins to weaken. Additional heavy precipitation is also forecast to affect the Alaska Panhandle on Wednesday. The chance of heavy rain should generally decrease during the Christmas holiday along the entire stretch of the southern coastal sections but a couple of smaller scale cyclones could bring periods of enhanced precipitation near the Alaska Peninsula and Alaska Panhandle. By next weekend, the next large-scale cyclone is forecast to move from west to east across the Aleutians, where gale to storm force winds and periods of heavy precipitation appear likely. Milder than normal temperatures are forecast to overspread mainland Alaska by next Wednesday under an upper ridge. The mild conditions should continue through Christmas holiday, cooling down slightly to near normal during next weekend along the Alaska Peninsula. 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