Alaska Extended Forecast Discussion National Weather Service College Park MD 705 PM EDT Fri Jun 20 2025 Valid 12Z Tue 24 Jun 2025 - 12Z Sat 28 Jun 2025 ...General Overview... The persistent omega blocking pattern across the Alaskan domain is forecast to relax a bit beginning early next week. The now familiar upper-level anticyclone centered over mainland Alaska is forecast to retreat southeastward as a deep upper low downstream moves away into the Pacific Northwest through the short-range period. It appears that the retreated upper high will reestablish near/over the northeast corner of Alaska early next week and then progress northward into the Arctic Ocean midweek. Meanwhile, the Bering low should slide very slowly east-southeast toward the eastern Aleutians through much of next week. Relatively weak waves or triple-point lows are forecast to eject eastward across the North Pacific and consolidate over the Gulf of Alaska by next weekend as the retreated upper ridge will remain anchored across northeastern Alaska and the Yukon territories. ...Guidance Evaluation/Preferences... Model guidance today shows general agreement on the aforementioned synoptic pattern evolution through next week. The deterministic model solutions from the GFS/EC/CMC begin to diverge a bit early next week regarding how much of the vorticity from the Bering Sea cyclone will be retained versus how much of it will be carried eastward into the Gulf of Alaska by the main jet stream across the North Pacific. The ensemble means are in better agreement with one another by way of more clearly indicating the possibility of a) the closed high reestablishing itself near the northeast corner of Alaska early next week, b) the slow southeastward progression of the Bering Sea low, and c) periodic eastward ejection of relatively weak waves or triple-point lows across the Gulf of Alaska toward the Panhandle through next week. It is noteworthy to mention that model guidance today, including the ensemble means, indicates that the upper anticyclone that is forecast to form near the northeast corner of Alaska early next week will progress farther northward into the Arctic Ocean through midweek. This is in contrast to yesterday's guidance which kept the anticyclone generally near the northeast Alaskan corner. The WPC Alaska medium-range forecast package was based on a consensus blend of 40% from the 12Z ECMWF/00Z EC mean, 40% from the 12Z GFS/GEFS, and 20% from the 12Z CMC/CMC mean, with a quick transition to mostly a blend of the ensemble means for Days 7 and 8. WPC continuity is well maintained. ...Weather/Hazards Highlights... With the anticipated retreat of the upper high over mainland Alaska, the afternoon heat across the Yukon Flats is forecast to moderate early next week, with high temperatures falling into the 70s. Underneath the retreating upper high, there will also be a lingering lower-level front across northern Alaska where scattered showers and thunderstorms are expected daily along the Brooks Range and across the eastern Interior including Fairbanks through next week. Daily rainfall amounts could locally exceed one inch across portions of the eastern Interior. The southern coastline and the Panhandle should be relatively dry as the medium-range begins next Tuesday. However, rain associated with the next cyclone should be moving through the Aleutians from west to east by then as rain chances increase along the Alaska Peninsula. Farther offshore, as low pressure waves/triple-point lows eject eastward across the Gulf of Alaska, rainy weather can be expected to reach the southern coastline and the Panhandle from west to east through the remainder of next week. The southwestern coastal areas, eastern Aleutians and the Peninsula can expect more widespread rainfall midweek next week when the Bering Sea low edges closer. By late next week, there is a potential for localized heavy rainfall across the climatologically rainy region of the Kenai Peninsula and eastern Alaska Peninsula as the Gulf of Alaska low is forecast to become more dominant. Temperature- wise, seasonable conditions are expected near the southern coast and the larger cities, with highs generally in the 50s and 60s. 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