Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 619 PM EDT Sun Oct 11 2020 Valid 12Z Thu Oct 15 2020 - 12Z Mon Oct 19 2020 ...Overview and Guidance/Predictability Assessment... A blend of overall compatible guidance of the 12 UTC GFS/ECMWF and GEFS/ECMWF ensemble means was used to provide a starting point for the WPC Alaskan medium range product suite along with the National Blend of Models. Most weighting was applied to the ECMWF ensemble mean and to a lesser extent the ECMWF. This emphasis again shifted the composite to the more amplified side of the full envelope of solutions for Alaskan mainland to Gulf of Alaska upper troughing this week. This still seems prudent given high upstream flow amplitude upstream. ...Weather/Threats Highlights.. Strong upper ridge amplification is expected up through the Bering Sea to into the Arctic Ocean early this week. This will allow Arctic flow energy to carve out an amplifying downstream upper trough down over an increasingly unsettled and cooled Interior through later week before the moderating main upper ridge is slated to shift eastward and inland. Forecast spread has improved, but guidance remains varied with the details of the upper trough. This Arctic energy may amplify sufficiently to overpower lead southern stream systems over the Gulf of Alaska, supporting phasing and low/system deepening. Southern and southeast Alaska will remain unsettled in this transitional pattern that should include heavier rains/snows. Meanwhile, forecast spread is relatively low and the guidance signal supports having the Aleutians/Gulf of Alaska turn stormy by next weekend into next week as amplified upper trough energies work deepening systems into the region from the Bering Sea and in lead flow up from the Pacific in the wake of the eastward shift of the main lead upper ridge. 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 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