Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 608 PM EST Sun Dec 29 2024 Valid 12Z Thu Jan 02 2025 - 12Z Mon Jan 06 2025 ...Overview with Guidance Evaluation and Preferences... Agreement among ensemble means from global models remain relatively well in depicting a tilted omega blocking pattern across the Alaskan domain gradually lifting northward across mainland Alaska and then evolving into a closed high over the Arctic Ocean during the medium-range forecast period. Much of mainland Alaska will then be under an upper-level col heading into the first weekend of 2025 as shown by the ensemble means. On the other hand, deterministic model outputs today continue to indicate the possibility for an upper-level vorticity center to develop over northwestern Alaska and then slide southwest into the Bering Sea during next weekend. There was also a separate upper high to develop over northeastern Siberia late this week to the southwest of the upper high over the Arctic Ocean. Meanwhile, the main cyclone tracks will remain well south of the Gulf of Alaska. These cyclones show a tendency to weaken as they head toward the Gulf. Ensemble means today continue to agree that a deeper cyclone will slide south of the Aleutians through the latter half of this week before edging north closer to the Aleutians by the following Monday. The WPC forecast was based on a consensus blend of the 12Z GFS/GEFS, 12Z ECMWF and 00Z/12Z EC mean, and the 12Z CMC/CMC mean. This solution maintained good continuity with the previous WPC forecast package. The 12Z ECMWF and the CMC both indicate a low pressure center to track west across the central Aleutians Wednesday to Thursday. This is in contrast to the EC-AIFS and the GFS which halt the westward progression of this low and then either dissipate it, or be absorbed by another cyclone to the southeast. ...Weather/Hazards Highlights... No hazardous weather is anticipated for the Alaskan domain through the medium-range forecast period. Much of mainland Alaska will be under a dry and persistent east to northeasterly flow near the surface with only modest amounts of precipitation along the southern coastlines including the Panhandle and the Aleutians. A relatively small cyclone should be pulling out of the central/eastern Aleutians on Thursday. By the latter half of this week, a general increase in precipitation chances and amounts can be expected for the western and central Aleutians when a deeper cyclone is predicted to slide to the south. In addition, this large cyclone will likely broaden and strengthen the northeasterly flow across the Bering Sea and through the Aleutians, with increasing chance of heavy precipitation possibly moving into eastern Aleutians and the Alaska Peninsula by late Sunday into Monday of next week. A persistent east to northeasterly flow being fed by a strengthening surface high pressure system centered over the Arctic Ocean (with central pressure possibly above 1050 mb) late this week will keep temperatures below normal for much of mainland Alaska. Minimum temperatures may drop below -40 degrees daily over the Yukon Flats. Above normal temperatures will be confined farther south across the Alaska Peninsula, all of the Aleutians, and along the southern coastlines and scattered locations for the Alaska Panhandle. Kong 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