Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 337 PM EDT Mon Jun 24 2019 Valid 12Z Fri Jun 28 2019 - 12Z Tue Jul 02 2019 A pattern change now appears likely across Alaska by late this week with the expected breakdown of the northern extent of the upper ridge, opening mainland Alaska up to stronger and more active westerly mid/upper-level flow. Models show relatively good consensus on a weakening frontal system crossing the Aleutians and moving into western mainland Alaska late this week, with the associated shortwave the mechanism for breaking down the northern extent of the upper ridge. A blend of the ECMWF and GFS served as a starting point for the forecast on day 4-5 (Fri-Sat), with a gradual trend to heavier weighting of ensemble means (ECENS and GEFS) starting on day 6 (Sun). The primary difference later in the period revolves around the eventual evolution of this shortwave as it moves east, with the ECMWF continuing to amplify the wave into the Gulf of Alaska by Sun night-Mon and the GFS showing a period of somewhat more zonal flow along the northern periphery of a more elongated upper ridge. Ensemble means suggest something in between these two scenarios may be a possibility, thus the use of majority ensemble means by the latter portion of the forecast period was warranted. This setup would bring an end to the drier conditions seen across much of Alaska recently, with an increase in moisture/showers for much of mainland and Southeast Alaska. Ryan 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 No significant hazards are expected over Alaska during this forecast period. 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