Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 632 PM EDT Mon Aug 17 2020 Valid 12Z Fri Aug 21 2020 - 12Z Tue Aug 25 2020 ...Guidance Evaluation and Preferences... Models/ensembles continued to relatively good consensus from recent days through the first part of the extended period (days 4-5), but showed more degradation compared to recent days later in the forecast period. A blend of the 12Z GFS/ECMWF was used during days 4-5 (Thu-Fri), with more weight on the ECMWF relative to the GFS. In the large scale sense, the solutions were not fundamentally different though the ECMWF favored closely with the ECENS/GEFS means, especially by days 6-8. While deterministic solutions showed greater differences, a blend of ensemble means likely represents the best consensus approach here by later in the forecast period, so higher weights of the ECENS and GEFS was incorporated. Thus, starting on day 6 (Sat) and continuing through day 8 (Mon), a gradual shift toward heavier use of ECENS/GEFS ensemble means was shown. ...Weather Highlights/Threats... For the forecast period, one low pressure system is forecast to cross the southern areas of the Gulf of Alaska through later this week, bringing widespread precipitation across the Panhandle. Then some periods of upper ridging across the Bering Sea and western Alaska will lead to drier periods, while wetter conditions prevail over the Panhandle and Southeast Alaska. From the mid to late forecast periods, another strong low pressure system to cross the Bering Sea, moving onshore over western Alaska into the early portions of the new week. Temperature wise, readings will favor above normal initially then begin to trend toward normal late in the period. Ryan/Taylor 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