Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 340 PM EDT Tue Jun 18 2019 Valid 12Z Sat Jun 22 2019 - 12Z Wed Jun 26 2019 An upper level low in the Gulf of Alaska to start the medium range period (Saturday) will shift south and eastward towards the Western U.S. coast as upper level ridging builds across the Peninsula into the Bering Sea and western mainland Alaska. Meanwhile, multiple shortwave perturbations will rotate around a broad upper level low anchored across the Kamchatka Peninsula of Russia to the far western Aleutians. A general consensus continues that this pattern will be slow to change through the medium range period as ensemble means hint at a developing omega block. There is good enough agreement between the deterministic runs of the 12z GFS/00z ECMWF/00z CMC to warrant a majority deterministic blend days 4 and 5. After this, increasing weighting of the ensemble means (GEFS/ECENS) was used to mitigate the smaller less predictable timing and detail differences. This resulted in a forecast close to yesterdays continuity. In terms of the sensible weather, most places across the Mainland should be fairly warm and dry, with the best chance for showers across the elevated terrain of southern Alaska. Increased rain chances will be possible across parts of the central and western Aleutians as southerly flow ahead of the broad upper level trough advects moisture into the region and a series of surface lows move nearby. Santorelli 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