Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 642 PM EDT Sun Jul 12 2020 Valid 12Z Thu Jul 16 2020 - 12Z Mon Jul 20 2020 ...Overview and Weather/Hazard Highlights... The flow pattern across the North Pacific is forecast to become gradually more amplified during the extended forecast period, with an upper trough strengthening from the Bering Sea south across the Aleutians, and an eastern Pacific ridge attempting to make some headway northward into the Gulf of Alaska. The amplifying flow will allow for increasing potential for arctic upper-level energy to move southward, with an upper low expected to move south toward the North Slope Fri-Sat, and another upper low forecast to dig south into the western Bering Sea Sun-Mon. The primary impact of the system affecting the North Slope will be on temperatures, with colder temperatures spreading across the region, and highs forecast to be 10-20 deg below average. In the meantime, a low pressure/frontal system is forecast to move east across the Alaska Peninsula Thu-Fri as it weakens, with another frontal wave following quickly behind it by Sat. These systems will keep rounds of showers in the picture from the Aleutians east into southern mainland Alaska from late this week into the weekend, with some potential for gusty winds at the coast. Shower activity may also be enhanced by Fri-Sat across portions of the Interior as moisture interacts with a weak stationary front. ...Guidance/Predictability Assessment... Model/ensemble consensus showed some improvement over recent days. The 12Z ECMWF seemed to be the deterministic solution most well-centered within the overall consensus through much of the extended forecast period. Thus, the ECMWF was heavily weighted in the WPC forecast during days 4-5 (Thu-Fri). After that, a gradual trend toward heavier weight on ensemble means (ECENS/NAEFS) was shown through time, with ensembles comprising a majority of the forecast by days 7-8 (Sun-Mon). 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 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