Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 147 PM EDT Mon Jul 02 2018 Valid 12Z Fri Jul 06 2018 - 12Z Tue Jul 10 2018 ...Pattern and Model Uncertainty... Guidance identifies three main medium range weather systems to impact Alaska and adjoining waters. This includes an upper trough extending from the Bering Sea southwest, the triple point low which forms east of what becomes Post-Tropical Cyclone Prapiroon that moves by southern AK into northwest Canada, and a cold front sweeping in from the north at the southern edge of the northern stream of the Westerlies. For the most part, the guidance is in very good agreement on system progression/depth. To deal with lingering detail issues, a compromise of the 00z UKMET, 00z ECMWF, 00z Canadian, and 06z GFS were used for pressures, 500 hPa heights, and winds for Thursday night into early Saturday. Thereafter, a slowly increasing percentage of the 00z NAEFS/00z ECMWF ensemble means was used, which reached 50% of the blend by July 11/00z. The remainder of the grids came from an even blend of deterministic (00Z Canadian, 00z ECMWF, 06z & 12z GFS runs) and ensemble mean (00z ECMWF & 00z NAEFS mean) guidance. ...Weather highlights.. With Prapiroon's triple point low approaching the state, rain chances increase from Thursday night/Friday in the Aleutians and across southern Alaska and the AK panhandle Saturday into Tuesday. Precipitation is expected to be moderate to heavy, with 1-2" of rain per day (and locally higher amounts) with the cyclone as it moves by southern AK. The approach of the low leads to increasing cloudiness early on, and skies should remain mostly cloudy through much of the period. Roth WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html