Alaska Extended Forecast Discussion National Weather Service College Park MD 759 PM EDT Fri Sep 5 2025 Valid 12Z Tue 09 Sep 2025 - 12Z Sat 13 Sep 2025 ...A deep cyclone will bring a round of rain and wind from the Aleutians to the Southern Coast and Southeast... ...Guidance Evaluation/Preferences... The main feature of interest through the medium range period will be a deepening cyclone which is forecast to track near or along the Aleutians. Since yesterday, global models have shown a significant shift in the forecast track of the cyclone. This shift has resulted in a track that brings the cyclone center north of the Aleutians from yesterday, to one that passes south of the islands today. This flippant behavior appears to stem from an ongoing difficulties for the models to resolve the complex interaction between Tropical Storm Peipah and an upper-level trough currently moving east of Japan. Model guidance agrees that this cyclone is not directly associated with the tropical storm vortex itself but amplifies from a triple-point low associated with extratropical transition of the tropical storm. In any event, toward the end of next week, ensemble means are showing good agreement for the cyclone to slow down as it heads into the Gulf of Alaska. As a result of the shift in the guidance, today's WPC forecast package requires a significant southward shift of the cyclone track through the medium-range period. The model blend comprises 40% of the 12Z GFS/GEFS, 40% of the 12Z ECMWF and 00Z/12Z EC mean, as well as 20% from the 12Z CMC/CMC mean, with a larger proportion from the ensemble means toward Day 8. ...Weather/Hazards Highlights... The medium-range period will begin on Tuesday with a dissipating cyclone over mainland Alaska, with a period of snow ending across the eastern portion of the North Slope as rain becomes more scattered across the eastern and southern mainland. Meanwhile, wind and rain associated with the deepening cyclone will likely impact the Aleutians from west to east across the Aleutians into the Peninsula through midweek next week. Even though the exact track of the cyclone remains subject to change, there will be a good chance for gap winds to develop on the back side of the cyclone which could extend into late next week as the cyclone slows down over the Gulf of Alaska. Rainfall-wise, a more southern track may spare the Aleutians from the impacts of the heaviest rains from this cyclone. Nevertheless, moderate to heavy rain is still expected for at least the western portion of the Aleutians early next week. Along the southern coastline, heavy rainfall is expected to linger with only a slow eastward progression toward the northern end of the Panhandle by late next week. Also by late next week, ensemble means show good agreement that a weaker low pressure wave behind the main cyclone will spread the next round of light to moderate rain into the Aleutians. Temperature-wise, much of Alaska will trend colder next week underneath of upper level troughing. Southeast Alaska and the Panhandle region look to be near or above normal given underneath of stronger upper level ridging. 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