Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 558 PM EST Mon Dec 30 2024 Valid 12Z Fri Jan 03 2025 - 12Z Tue Jan 07 2025 ...Heavy precipitation possible late this weekend into early next week for the eastern portion of the Alaska Peninsula into the Kenai Peninsula... ...Overview with Guidance Evaluation and Preferences... Global models are in good agreement that 2025 will begin with a cold and dry note across much of the Alaskan domain as mainland Alaska will remain underneath a col at the 500mb level, anchored by a couple of a closed highs situated over the Arctic Ocean and northeastern Siberia. Deterministic model outputs continue to indicate that subtle upper-level vorticity center(s) will develop over northwestern Alaska and then slide southwest into the Bering Sea during next weekend. Meanwhile, ensemble means continue to agree that a deeper cyclone will slide south of the Aleutians through the latter half of the week before edging north toward and into the Aleutians by early next week. On the other hand, deterministic model guidance are indicating that disturbances within the frontal zone/triple-point on the eastern flank of the large cyclone will move north toward the vicinity of eastern Aleutians to the Alaska Peninsula beginning this weekend into early next week. Agreement on the details of these disturbances are relatively poor at this point in time. 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. ...Weather/Hazards Highlights... 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. By the time the medium-range period begins later this week, a general increase in precipitation chances and amounts can be expected for the western and central Aleutians when a deeper cyclone from the Pacific is forecast to edge closer to the island chain from the southwest. 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 moving into eastern Aleutians and the Alaska Peninsula by late Sunday. Monday into Tuesday of next week should see the heavy precipitation pushing gradually northward through the eastern portion of the Alaska Peninsula and Kenai Peninsula. Uncertainty on the details of the track and intensity of smaller-scale cyclones coming up from the south leads to uncertainty on the details in the timing of the heavy precipitation at this point in time. The persistent east to northeasterly flow being fed by a strong surface high pressure system centered over the Arctic Ocean (with central pressure possibly above 1050 mb) late this week will keep temperatures below to locally well below normal for much of mainland Alaska. Minimum temperatures may drop below -40 degrees over the Yukon Flats. Above normal temperatures initially confined farther south across the Alaska Peninsula and the Aleutians will gradually spread toward the north and east into mainland Alaska early next week as the aforementioned large cyclone gradually pushes into the Aleutians. A warming trend can also be expected from the southern coastlines to the Alaska Panhandle with modest precipitation edging in from the west by early next week. 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