Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 636 PM EST Wed Dec 01 2021 Valid 12Z Sun Dec 05 2021 - 12Z Thu Dec 09 2021 ...Large storm system to bring heavy snow and gusty winds to parts of western Alaska Sunday-Monday... ...Overview and Guidance Evaluation/Preferences... Parts of the Alaska region should become increasingly active through this weekend and into early next week as amplified troughing brings a deep cyclone across the Bering Sea and into western Alaska by next Monday. The system should weaken as it tracks through the Mainland though additional triple point development along the Gulf Coast should send a cold front towards the Panhandle region mid week. Meanwhile, an additional shortwave tracking towards the Aleutians next Wednesday into Thursday may send another deep low pressure system into the southern/western Bering Sea. In general, the guidance shows relatively good agreement through the first couple days of the period on the overall synoptic pattern, with the exception of the 12z CMC which was noticeably slower/southwest of the better consensus for the Bering Sea/western Alaskan low. By day 6/Tuesday, more of the typical timing and detail differences begins to arise, especially surrounding the next low towards the Aleutians and possibly into the Bering Sea. The GFS/CMC and ensemble means support this low lifting into the Bering Sea, while the 12z ECMWF keeps the low well south of the Aleutians. The WPC forecast progs used a deterministic model blend (minus the 12z CMC) for days 4-5, gradually increasing weighting of the ensemble means thereafter to help smooth out the smaller scale uncertainties which will need more time to resolve. This approach maintains good continuity with yesterday's WPC forecasts as well. ...Weather/Hazard Highlights... The Bering Sea cyclone will usher in a much more active weather pattern across Alaska consisting of windy and snow conditions. Much of western Alaska will experience snow Sunday into Monday, with the greatest threat across parts of the Seward Peninsula and southwestern Alaska. Current guidance suggests some locations could see upwards of a foot of snow, along with a period of gusty winds as the low moves inland on Monday. Increasingly wet weather will also move into parts of the Southern Coast and southeast Alaska Monday into Tuesday again with a threat for locally heavy snows, especially across the favorable terrain. The cold front propagating through the Gulf should bring increased rain chances to the Panhandle mid week next week with rain again threatening the Aleutians as well with the next low pressure system into the region. After a period of much below normal temperatures, conditions should finally begin to moderate from west to east by the start of the extended period on Sunday as the Bering Sea low brings milder air in from the south. By next Monday, much of interior and northern Alaska should see temperatures near or above normal, with the greatest anomalies likely across parts of western Alaska and the North Slope region. Santorelli Hazards: - Heavy snow across portions of southwestern Alaska, Mon, Dec 6. - High winds across portions of Seward Peninsula in Alaska, Sun, Dec 5. - Much below normal temperatures across portions of central and eastern Alaska, Sat, Dec 4. 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