Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EDT Sat Sep 05 2020 Valid 12Z Wed Sep 09 2020 - 12Z Sun Sep 13 2020 ...Weather/Threats Highlights and Guidance/Predictability Assessment... Stormy upper troughing and short range focusing unsettled weather over the Bering Sea moves inland over the Interior Wednesday-Thursday, pushing robustly through an ambient amplified upper ridge. In the wake of this heading into the weekend, Arctic stream upper troughing and a frontal push works into the North Slope. Meanwhile, a separate and dynamic southern storm track sets up across the Pacific. Details and system transitions with lead system energies within this flow are more complex, lowering forecast confidence on the main weather focus up into the Gulf of Alaska. However, there is a decent guidance signal for flow amplification in this stream in tandem with some infusion of amplified northern stream energy. This occurs with the slated approach of the deepened extratropical low associated with northward lifting Typhoon Haishen from a current position to the south of Japan/Korea. This deep low may reach the Aleutians next weekend and produce quite a threat of high winds/waves and enhanced wrapping rains. Models and ensembles offer a reasonably similar larger scale pattern evolution, but differ with embedded system details and offer less than stellar continuity. The 12 UTC ECMWF solution seems overall the closest model fit with the 12 UTC GEFS/ECMWF ensemble means and a composite blend of these was used for the basis of the WPC medium range product suite along with the 19 UTC National Blend of Models. 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