Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 606 PM EST Mon Dec 27 2021 Valid 12Z Fri Dec 31 2021 - 12Z Tue Jan 04 2022 ...Overview... A deepening low pressure will track from the eastern Bering Sea across the southern mainland into the Gulf of Alaska this weekend, bringing widespread snow to southern mainland and the southeastern areas. In its wake, a pronounced blocky pattern is forecast to develop which should allow for much below normal temperatures to dig southward across the southern, eastern, and southeastern areas. ...Overview and Guidance Evaluation... Today's 12Z model guidance suite showed fairly good agreement and predictability throughout the period with the expected evolution toward a more amplified pattern. At the start of the period /12-31/, an area of low pressure over the eastern Bering shows good agreement between the latest deterministic model guidance and that low is forecast to track through southern Alaska into the Gulf of Alaska. As it does so, the upper level pattern is forecast to become more blocky. An eastern Gulf upper trough deepens and the whole system slowly occludes through day 6. This scenario had good agreement such that a near equal multi-model blend was incorporated for days 4-6. Beyond that time frame, the signal for a pronounced and highly amplified pattern is increasing with impressive height anomalies. This setup favors strong/cold high pressure over the eastern mainland or northwest Canada with some of the deterministic guidance hinting at 1050+ mb high early next week. The days 6-7 blend incorporated more of the ECENS and GEFS means to account for the increasing model spread in that time frame. ...Weather/Hazard Highlights... A surface low will track through the Bering Sea, bringing widespread light to moderate precipitation inland across southwest to south-central Alaska while a deeper fetch of moisture will support heavy snow for much of the Panhandle on Friday into Saturday. Amounts of up to or exceeding a foot are possible, though right along the coast, totals may be lighter as precipitation mixes with rain. Behind this feature, a strong Arctic airmass will pour southward bringing much below normal temperatures to eastern sections of Interior Alaska, much of southwestern and south-central Alaska and possibly into the Panhandle for early next week. Taylor Hazards for Alaska for Dec 31 - Jan 4: - Heavy snow across portions of the Alaska Panhandle and mainland Alaska, Fri-Sat, Dec 31-Jan 1. - High winds across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Jan 1-Jan 2. - High winds across portions of the Aleutians, Thu, Dec 30. - Much below normal temperatures across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Jan 2-Jan 3. 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