Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 529 PM EST Sun Dec 26 2021 Valid 12Z Thu Dec 30 2021 - 12Z Mon Jan 3 2022 ...Overview... The block pattern with the large upper ridge and surface high over the northeast Pacific through the middle of the week is expected to gradually weaken and settle southward by Friday. A well defined low pressure system from the Bering and the Aleutians will likely bring widespread snow for much of the mainland to close out the week. By next weekend, the ridge is expected to build back northward across the Aleutians/Bering with perhaps another blocky pattern developing. ...Overview and Guidance Evaluation... The 12Z model guidance suite has a good overall depiction of the large scale pattern through the extended range period as things become more amplified. The guidance is consistent in breaking down the North Pacific ridge by the end of the week with a potent storm system tracking eastward from the Bering. Both the 6Z/12Z runs of the GFS have been faster with the disturbance entering the Gulf by Saturday, and the CMC a bit slower and weaker. By Sunday, the upper ridge over the Bering kicks into high gear along with a deepening trough over the eastern Gulf. The 12Z ECMWF even suggests an anomalous closed upper high over the central Bering by next Monday, and this would basically be a westward displaced -EPO. This could easily result in a renewed blocky pattern across the Alaska domain. Taking these factors into account, a multi-deterministic blend was used through early Saturday as a starting point in the forecast process, and slightly greater use of the ensemble means while retaining primarily some of the 12Z ECMWF along with some previous WPC continuity for Sunday and into Monday. ...Weather/Hazard Highlights... Widespread light to moderate snow appears likely across a majority of the southern half of the state for the end of the week, and maybe warm enough for rain for the immediate coastal areas along the eastern Aleutians to the Kenai Peninsula, as an organized low approaches from the Bering. The surface low is expected to intensify over northern Gulf by Saturday morning, and thus some areas of heavy precipitation will likely develop over the southeast Panhandle region. A drier trend should ensue for most of the state by Sunday and beyond. In terms of temperatures, much of the southern portion of the Interior will get to enjoy more above average temperatures for the end of the week with less of an inversion in place and highs running 10-20 degrees above normal for many areas. Unlike last week, the Arctic Coast and the North Slope will miss out on the milder temperatures as readings will likely stay below zero from the Brooks Range and points northward. With the exception of the Aleutians, bitterly cold temperatures are likely to make a return to much of the state to begin 2022. Hamrick 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