Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 508 PM EST Fri Dec 24 2021 Valid 12Z Tue Dec 28 2021 - 12Z Sat Jan 1 2022 ...Overview... The block pattern with the large upper ridge and surface high over the northeast Pacific early in the week is expected to gradually weaken and settle southward by the middle to end of the week. This will result in the transition from an amplified to a more quasi-zonal flow pattern by the end of the forecast period. 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, with perhaps a third system over the Gulf by Friday or Saturday. ...Overview and Guidance Evaluation... Models and ensembles are in excellent synoptic scale agreement through Wednesday across the Alaska domain. The 12Z GFS is slightly stronger with the shortwave trough entering the northern Gulf Wednesday night, but is similar to the CMC and ECMWF regarding timing. The main difference is the much faster UKMET, which is not favored given its lack of ensemble support. There is reasonable agreement with the next organized storm emerging from the Bering late in the week, and also across the Arctic with a broad upper low in place. The ECMWF is stronger with a trailing disturbance on New Year's Day across the Aleutians. Taking these factors into account, a GFS/ECMWF/CMC blend was used through mid-week, and slightly greater use of the ensemble means while retaining some of the CMC/ECMWF/GFS along with some previous WPC continuity to close out the week. ...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 20+ degrees above normal for many areas. Unlike last week, the Arctic Coast and the North Slope may miss out on the milder temperatures as readings will likely stay closer to climatological averages with the storm track staying farther south. Below average temperatures remain likely for much of the southeast Panhandle region through the middle of the week with an arctic air mass entrenched over western Canada. Hamrick Hazards: - Heavy precipitation across portions of the Alaska Panhandle, Wed, Dec 29. - Heavy snow across portions of mainland Alaska, Tue, Dec 28. - Much below normal temperatures across portions of the Alaska Panhandle, Mon-Tue, Dec 27-Dec 28. 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