Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 639 PM EDT Fri Aug 20 2021 Valid 12Z Tue Aug 24 2021 - 12Z Sat Aug 28 2021 ...An Active Weather Regime for Alaska.. ...Guidance/Predictability Evaluation... 12 UTC GFS/ECMWF solutions seem reasonably well clustered days 3-7 across much of Alaska and adjoining waters, albeit with the ECMWF more amplified with time into the Interior within an energetic and unsettled Arctic stream. Underneath in an also active mid-upper latitude stream from the Bering Sea and northern Pacific into the Gulf of Alaska, a blend of the more amplified 12 UTC GFS/ECMWF seems to better fit upstream flow ridge amplitude than the somewhat more progressive solutions from the 12 UTC Canadian/UKMET, GEFS/ECMWF ensemble means and WPC continuity. Accordingly and considering overall forecast spread, the WPC Alaskan medium range product suite was primarily derived from a blend of the GFS/ECMWF, but also smaller inputs of the GEFS/ECMWF ensemble means to address lingering uncertainties. ...Pattern Overview and Weather/Threats Highlights... An amplified flow pattern next week should maintain wet and unsettled conditions across much of Alaska. Southerly fetch ahead of a series of energetic systems set to work across the Gulf next week will direct significant moisture into southern Alaska fueling moderate to heavy rainfall from parts of the southern Coast to the Panhandle. Higher elevations will also see measurable snowfall. Meanwhile, potent shortwaves interacting with a persistent Arctic frontal boundary will allow organized precipitation periodically across northern and Interior Alaska. In particular, an organized low pressure system reaching northwest Alaska Thursday will bring increased chances for enhanced rainfall inland into later next week. The pattern supports below normal maximum temperatures for much of Alaska. Schichtel Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Tue-Wed, Aug 24-Aug 25. - Heavy rain across portions of mainland Alaska, Mon, Aug 23. - 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