Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 424 PM EDT Sat Jul 18 2020 Valid 12Z Wed Jul 22 2020 - 12Z Sun Jul 26 2020 The forecast for the latter portion of next week is for persistent mid-level height anomalies across mainland Alaska associated with an arctic upper low and trough situated north of the state, with positive height anomalies over the Aleutians turning negative with time. The 12z GEFS shows a west drift of the trough axis with time, which next weekend opens up the possibility of heights rising and temperatures moderating back towards 30 year normal over the AK panhandle/southeast AK. The primary storm system in the medium range is expected to form over the western Bering Sea and is expected to drift slowly towards the east in the mid to latter portions of next week. The 00z ECMWF was offset from the majority cluster and the new 12z run has come into better agreement with both the 12z GFS and its own 00z ECMWF Ensemble Mean. With increased clustering among solutions, a blend of the 12z ECMWF/00z ECMWF Ensemble Mean, 12z GEFS Mean, and 12z GFS was used. The CMC was more progressive with the system and also for heights to lower in the Gulf of AK/Kodiak/AK peninsula days 7-8, so the Canadian was not included in the blend given the majority of solutions are high amplitude and slow. The ECMWF/UKMET/Canadian cluster better with the 00z ECMWF Ensemble Mean with low pressure in the Arctic Ocean, so the 12z GFS was given less weight there. Finally, on days 7-8, the GFS produces a triple point low south of the Aleutians and moves the low towards the Gulf of AK Day 8. Given the GFS was stronger than other solutions, the GFS was given less weight, with the use of the 12z GEFS Mean to mitigate uncertainties, along with the 00z ECMWF Mean and operational 12z ECMWF. Petersen 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