Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 635 PM EDT Sun Sep 06 2020 Valid 12Z Thu Sep 10 2020 - 12Z Mon Sep 14 2020 ...Weather/Threats Highlights and Guidance/Predictability Assessment... An energetic upper trough and surface frontal system/weather focus will exit the Interior Thursday. In the wake of this feature, upper troughing underneath a closed Arctic Sea low will force a cooling front across an unsettled North Slope and Interior. Meanwhile, a separate and dynamic storm track will setup over the northern Pacific and southern Bering Sea/Aleutians with ample energy from an upper latitude closed trough/low. Details and system transitions with lead system energies within this flow are complex, lowering forecast confidence on the main weather focus up into the Gulf of Alaska. There is also an uncertain signal with an infusion of energy/moisture associated with the extratropical evolution of current west Pacific Typhoon Haishen from the far western Pacific then northeast Asia. This may lead to a late week threat of high winds/waves and heavy wrapping rains for the Bering Sea/Aleutians to then spread into southwest/southern Alaska next weekend/Monday. 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 GFS 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. Ensemble weighting in the composite blend was increased by the weekend as per rapidly increasing forecast spread. 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