Alaska Extended Forecast Discussion National Weather Service College Park MD 656 PM EDT Tue Sep 16 2025 Valid 12Z Sat 20 Sep 2025 - 12Z Wed 24 Sep 2025 ***Periods of heavy rain and gale force winds expected from the Prince William Sound to Southeast Alaska*** ...General Overview... A rather unsettled weather pattern will remain across southern Alaska and the Panhandle region as a broad upper level low becomes anchored in place across the northern Gulf by the weekend. Multiple shortwave impulses are expected to pivot around the southern and eastern periphery of that low and bring multiple rounds of rain and gusty winds. This will likely have some staying power going into early next week as well. A cold front is expected to slowly sink south across the mainland and bring a steady cooling trend over the next week. ...Guidance Evaluation/Preferences... The 12Z model guidance suite initially has a good overall depiction on the overall weather pattern across the domain for Friday into Saturday. There has been a trend for a stronger low crossing the north Pacific into the eastern Gulf Sunday through late Monday, and this is most evident among the GFS/ECMWF/UKMET guidance, whereas the CMC is considerably weaker with that low, and the UKMET is most progressive with it. The GFS remains stronger with a Bering Sea trough on Tuesday, similar to yesterday. Model spread increases a lot by the end of the forecast period, especially with the next storm system near the Aleutians. The GFS is way weaker with this low, compared to the non-NCEP guidance that maintains better continuity with yesterday's forecast. Overall, that low has trended slower over the past 24 hours. A general deterministic model blend suffices as a good starting point for Saturday, and then the ensemble means were gradually increased to about half by next Wednesday. ...Weather/Hazards Highlights... Several inches of rainfall are likely from the Prince William Sound to Southeast Alaska as multiple surges of moisture move into the region, with the highest totals across the windward terrain from the St. Elias Mountains to the windward terrain of the southeast Panhandle. Strong winds of gale force are likely for the near shore waters owing to enhancement of the coastal barrier jet for these same general areas, especially with the low pressure system arriving on Monday with gusts in excess of 50 mph at times. This will result in hazardous boating conditions for the coastal waters. In terms of temperatures, a gradual cooling trend is expected to commence across the mainland as a polar front slowly sinks southward through Monday, with some subfreezing overnight lows possible across portions of the Interior by the middle of next week, and widespread subfreezing lows north of the Brooks Range. Hamrick 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