Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 651 PM EDT Sat Aug 21 2021 Valid 12Z Wed Aug 25 2021 - 12Z Sun Aug 29 2021 ...An Active Weather Regime for Alaska.. ...Guidance/Predictability Evaluation... The latest 12 UTC GFS/ECMWF/Canadian solutions seem reasonably well clustered days 3-7 across much of Alaska and adjoining waters, albeit with the ECMWF/Canadian 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 and now Canadian seems to better fit upstream flow ridge amplitude than the somewhat more progressive solutions from the 12 UTC UKMET and GEFS ensemble mean. The 12 UTC ECMWF ensemble mean has also now trended toward the suggested WPC guidance blend. Accordingly and considering overall forecast spread, the WPC Alaskan medium range product suite was primarily derived from a blend of the GFS/ECMWF/Canadian, but also smaller inputs of the GEFS and now especially the 12 UTC ECMWF ensemble mean to address lingering uncertainties days 7/8. This forecast plan maintains good WPC product continuity. ...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 of Alaska 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. A lead system over the northern and eastern Gulf midweek will give way to a more complex system working from the Aleutians midweek that is expected to solidify across the northern Gulf into later next week/weekend. 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 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