Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 348 PM EDT Mon Sep 02 2019 Valid 12Z Fri Sep 06 2019 - 12Z Tue Sep 10 2019 Models showed reasonably good consensus during the first half of the extended period, and a blend of the GFS and ECMWF served as a good forecast starting point across Alaska for days 4-5 (Fri-Sat). This consensus solution resulted in relatively small changes to continuity. A low pressure system crossing the eastern Aleutians and moving into the Bering Sea Fri-Sat has shown a slight northward shift in the model consensus compared to 24 hours ago, and this trend was reflected in the latest forecast. Models continue to support the idea of a triple point low developing across the western Gulf of Alaska by Sun as the system quickly begins to weaken. This system may produce heavy rainfall across portions of the Alaska Peninsula and southern mainland Alaska Fri-Sat. Shifted to gradually heavier ensemble mean weighting for days 6-8 (Sun-Tue). Model differences begin to increase substantially by that time frame with another low pressure system crossing the Aleutians and forecast to move into the eastern Bering Sea. The forecast for this system was kept relatively close to the ensemble means. Finally, the GFS brings a very intense low pressure system into the western Bering Sea by day 8, likely a post-tropical version of Tropical Storm Lingling (currently across the west central Pacific). Given very high model/ensemble spread, the GFS solution was not reflected in the forecast at this time. Downstream of the active storm track across the Bering/Aleutians, models show general consensus that an upper-level ridge axis should remain in place across eastern mainland Alaska through the extended period. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Heavy rain across portions of mainland Alaska, Fri-Sat, Sep 6-Sep 7. 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