Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 331 PM EDT Thu Aug 29 2019 Valid 12Z Mon Sep 02 2019 - 12Z Fri Sep 06 2019 ...Potent eastern Bering Sea storm threatens mainland into early next week... Models and ensembles still strongly agree that a potent low pressure system will lift through the eastern Bering Sea early next week as upper ridging over the eastern mainland slips eastward into Canada. A blend of the quite well clustered and reasonable 12 UTC GFS and ECMWF was used in this period of above average forecast confidence. This system will be a hazard for maritime interests and a downstream heavy weather/precipitation threat to focus into western/southwestern Alaska and across the southern Alaska tier considering moisture transport and dynamic closed low/trough support aloft. There is now better guidance signal for second low system development and rotation on the backside of this lead storm to mainly effect maritime interests over the central and northern Bering Sea/Bering Strait. Forecast spread increases by day 7/8, suggesting transition to usage of just the more compatable ensemble means at these longer time frames. Upper trough amplification by then into the Aleutians and southern Bering Sea seems to support a pattern favorable for additional organized low system developments and heavy weather potential. Schichtel 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, Sun-Mon, Sep 1-Sep 2. - High winds across portions of mainland Alaska and the Aleutians, Sun, Sep 1. 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