Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 646 PM EDT Sun Jun 13 2021 Valid 12Z Thu Jun 17 2021 - 12Z Mon Jun 21 2021 ...Guidance/Predictability Evaluation... The WPC Alaskan medium range product suite was primarily derived from a blend of well clustered guidance of the 12 UTC GFS/ECMWF, 12 UTC GEFS/NAEFS/ECMWF ensemble means and the 19 UTC National Blend of Models Day 4-6 (Thursday-Saturday). The 12 UTC GFS/ECMWF are better clustered than yesterday, so applied higher blend influence in this period. The 12 UTC ECMWF is better clustered with the 12 UTC GEFS/NAEFS/ECMWF ensemble means for days 6/7, so that blend was then used as a basis for the WPC forecast. The larger scale pattern evolution and storm track still seems solid in guidance. However, given the recent run to run model sensitivity/continuity issues with many flow embedded systems, the newly improved forecast spread probably needs to be maintained for more model runs before bolstering confidence too much with these small-mid scale features. ...Weather/Threats Highlights... A stable, shielding and warming mean upper ridge is expected to settle over much of the Interior and North Slope for much of this forecast period. Meanwhile, a persistent and active storm track will progress near/just south of the Aleutians and into the Gulf of Alaska. In this flow, a complex and uncertain series of potentially deep lows and frontal systems may focus quite unsettled maritime and periodic rains and winds into southwest Alaska, the Alaskan peninsula and southern and southeast Alaska. 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