Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 454 PM EDT Wed Aug 10 2022 Valid 12Z Sun Aug 14 2022 - 12Z Thu Aug 18 2022 ...Cool/wet-to-snowy pattern for August returns this weekend across the North while rounds of heavy rainfall likely across the South & Panhandle... ...Guidance/Predictability Assessment... The guidance shows better than usual agreement into early next week as an upper trough closes off an upper level center across western AK and a cyclone yo-yos between AK and the northeast Pacific. Since agreement was so good early on, used a compromise of the 12z GFS, 12z Canadian, 12z UKMET, and 12z ECMWF for the pressures/500 hPa heights/winds early next week. Starting late Monday, both the 12z ECMWF/12z Canadian retrograde the western AK mid-level cyclone westward which allow it to capture/merge with another system to the southwest and race a new cyclone towards western AK. While the 12z NAEFS mean and 00z ECMWF offered some support aloft, their surface lows were slower similar to the 12z GFS. Used a combination of the 00z ECMWF/12z GFS to deal with this issue as well as the 00z ECMWF/12z NAEFS means for the solution mid next week which led to reasonable continuity for a forecast at that range. The grids were derived from the 19z NBM except the QPF, which weighted towards 12z GFS and 00z ECMWF guidance for realistic amplitudes. ...Sensible Weather... Cooler air from the Arctic is forecast to filter across the North by this weekend with high-elevation snow possible over the Brooks Range. Meanwhile, the greatest threat of heavy rain will be focused along the coastal sections and nearby high terrain of south and southeast Alaska and the AK panhandle from this weekend into mid next week with the passage and return of an occluded cyclone. This cyclone is forecast to wander south before returning north early to mid next week, generally maintaining its strength. Local amounts of 5"+ are possible from this system in the favored topography between late this week and mid next week. Meanwhile, the central portion of Alaska should be sheltered from significant rain chances. However, with the upper trough across the west and deep layer cyclone hovering near to offshore southern AK, much of the state should be cloudy. There might be windows of opportunity for partly cloudy skies in the west from time to time. Cool air from the Arctic will bring chilly conditions into the North Slope by the weekend with snowfall possible over the Brooks Range. The polar air is forecast to show limited southward penetration down the west coast but should remain across the North Slope into early next to mid next week. The interior will be mild to warm, with temperatures peaking in the 60s and 70s each day. Roth - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Wed, Aug 13-Aug 17. - Heavy snow across portions of mainland Alaska, Sat-Sun, Aug 13-Aug 14. 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