Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 528 PM EST Fri Dec 17 2021 Valid 12Z Tue Dec 21 2021 - 12Z Sat Dec 25 2021 ...Overview... The main theme going into next week will be a dominant upper ridge/surface high pressure over the North Pacific with multiple shortwaves/storm systems tracking around the northern and eastern periphery of the high. A slow moving polar low near 75-80 degrees north is also expected to slowly lift north across the Arctic Ocean and the ridge axis builds northward across the Bering and western Alaska by Christmas. A strong cold front is expected to cross most of the state by Tuesday and bring a return to colder temperatures after above average readings this weekend and Monday. ...Guidance Evaluation and Preferences... The 12Z model guidance suite is in good overall agreement on Tuesday across the Alaska domain, and there has been a trend for a stronger shortwave/surface low over the northeastern Gulf and southeast Panhandle region since yesterday, with the exception here being a weaker CMC solution. The upper high centered south of the Alaska Peninsula has the greatest model agreement through the extended forecast period, and should remain nearly anchored in place near 45N/160W. The polar low north of the Arctic Coast is also well represented by the guidance. Model differences become more noteworthy by Thursday with both timing and magnitude differences with shortwave energy emerging from eastern Siberia. Given the strong signal in the ensemble means for an elongated north-south ridge axis across the Bering late in the forecast period, and the potential for some blocking to develop, the incursion of stormy weather from the western Bering and eastern Siberia should hold off through the end of the week. Taking these factors into account, the WPC forecast is primarily derived from a UKMET/GFS/ECMWF/ensemble mean blend through Wednesday night, and then ECMWF/some GFS/increased ensemble means thereafter. ...Weather/Hazard Highlights... Temperatures are expected to be pleasant for this time of year and thus well above average across much of the mainland to begin the week, with the potential for some daily record highs to be established. Some inland locations that have been below freezing for many weeks might get readings above 32 degrees briefly early in the week before reality sets in after a strong cold front moves through. Strong and gusty winds are also likely for portions of the Arctic Coast through midweek. Latest model guidance suggests that warmer weather may try to make a return to portions of the Interior by the end of the week, and this would likely be accompanied by warm air advection snow from the western mainland to the Brooks Range, with the potential for several inches of accumulation. Lingering rain/snow showers are likely across the southeast Panhandle region on Tuesday as the low pressure system departs the region. Hamrick Hazards: - Heavy snow across portions of mainland Alaska, Mon, Dec 20. - High winds across portions of mainland Alaska, Tue-Fri, Dec 21-Dec 24. - High winds across portions of mainland Alaska, Tue-Wed, Dec 21-Dec 22. 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