Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 644 PM EDT Mon Aug 23 2021 Valid 12Z Fri Aug 27 2021 - 12Z Tue Aug 31 2021 ...Guidance/Predictability Evaluation... The WPC Alaskan medium range product suite was primarily derived from a composite blend of reasonably well clustered solutions from the 12 UTC GFS/ECMWF/UKMET/Canadian Day4/Fri and then the ECMWF/UKMET and ensemble means Day 5/Saturday. The GEFS/NAEFS/ECMWF ensemble means seem much more run to run stable into the days 6-8 period and are preferred amid quickly growing model forecast spread and uncertainty. ...Pattern Overview and Weather/Threats Highlights... Upper energies interacting with Arctic frontal boundaries will support organized precipitation across northern and Interior Alaska. In particular, an organized low pressure system tracking to the north of the North Slope by Friday will bring increased chances for enhanced precipitation inland across the North Slope/Brooks Range and the eastern Interior. Additionally energies rotating down from the Arctic Ocean will also favor organized precipitation underneath into the North Slope into the weekend. This pattern supports below normal maximum temperatures down across much of Alaska. Meanwhile to the south, an energetic system will track from south of the Aleutians/AKpen Friday to the northeastern Gulf into next weekend. This system offers a maritime threat along with some enhanced weekend precipitation focus, mainly into Southeast AK. Upstream, there is much more uncertainty with system development and progression days 6-8 for Pacific systems working to the Aleutians/Bering Sea. Schichtel Hazards: - High significant wave heights for coastal portions of mainland Alaska, Thu, Aug 26. Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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