Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 756 PM EDT Mon Sep 5 2022 Valid 12Z Fri Sep 9 2022 - 12Z Tue Sep 13 2022 ***Heavy precipitation/wind/atmospheric river threat inland from the Gulf of Alaska to south-central/southeast Alaska and the Interior on Friday*** ...Guidance/Predictability Assessment... The 12Z guidance suite initially has a good overall depiction of the weakening upper low centered over western Alaska on Friday and the trailing trough/front across the Gulf region. By Saturday, the GFS becomes more amplified with the system crossing the Bering and is slower than the better clustered CMC/ECMWF/UKMET solutions, and the GFS is also displaced to the northeast with the upper ridge across the Arctic this weekend. A general blend of the aforementioned operational models sufficed as a good starting point in the forecast process through early Sunday, and this maintained decent overall WPC continuity. By early next week, the ensemble means favor upper level troughing building back in across the Bering and western Alaska, with the CMC and ECMWF fairly well aligned with the GEFS and ECENS. To account for increasing mesoscale uncertainties, more of the ensemble means were incorporated for the Day 7 and 8 time periods. ...Sensible Weather and Potential Hazards... The main emphasis of the forecast going into the end of this week and into the weekend will be the evolution of shortwaves and embedded lows digging from the Bering to just south of the Aleutians, along with how they may interact with North Pacific flow/surface low pressure systems. Heavy rainfall associated with a probable atmospheric river on Friday is expected to result in several inches of rain from the eastern Kenai Peninsula to the St. Elias Mountains, and some flooding issues will be possible with enhanced run-off. Another round of moderate to heavy rain is on the horizon for early next week across the south-central mainland, with daily 1-2 inch totals possible each day. Farther north, several inches of snow is likely for the higher terrain of the Brooks Range as moisture lifts northward ahead of a strong low pressure system, and moderate rain for the valley locations. Gusty winds and rough seas will also be commonplace across the Aleutians and coastal areas as multiple low pressure systems affect the region. Hamrick Hazards: -Heavy rain across portions of the Alaska Panhandle and southern mainland Alaska, Thu-Fri, Sep 8-Sep 9. 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