Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 521 PM EST Sat Dec 25 2021 Valid 12Z Wed Dec 29 2021 - 12Z Sun Jan 2 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. Two well defined low pressure systems from the Bering and the Aleutians will likely bring a few rounds of snow for much of the mainland. 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... Models and ensembles are in reasonably good synoptic scale agreement through most of the forecast period across the Alaska domain. The main exception to this is the 12Z CMC that is likely too flat with the shortwave trough crossing southern Alaska as early as Wednesday, and also considerably slower with the next and larger storm system crossing the Aleutians by Thursday. The UKMET has trended closer in line with the model consensus compared to yesterday's much faster solution. By Friday night and into the weekend, the GFS becomes more amplified with the trough over the Gulf and this solution evolves into a big closed low, whereas the ensemble means would suggest this trough/upper low to be farther north and not quite as strong. Taking these factors into account, a GFS/ECMWF/UKMET blend was used through early Friday 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 New Year's weekend. ...Weather/Hazard Highlights... Periods of light to moderate snow, and heavy snow for mountainous areas, appears likely across a majority of the state for the Tuesday/Wednesday time period, and maybe warm enough for rain across the lower elevations of southwestern Alaska with strong warm air advection in place in the warm sector of the low. A second round of organized precip is also on the horizon for the end of the week as another low approaches from the Bering. Depending on what eventually develops over the northern Gulf by next Friday, some areas of heavy precipitation may develop over southern Alaska and the southeast Panhandle region. In terms of temperatures, much of the Interior will get to enjoy more above average temperatures for much of next 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 should miss out on the milder temperatures as readings will likely stay closer to climatological averages or slightly below with the storm track staying farther south. Below average 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