Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 641 PM EDT Sat Jul 11 2020 Valid 12Z Wed Jul 15 2020 - 12Z Sun Jul 19 2020 ...Overview and Weather/Hazard Highlights... A relatively progressive flow pattern looks to persist across the North Pacific through the first half of the extended forecast period, with Alaska on the northern periphery of this area. Ensemble guidance suggests a gradual amplification of the flow over time, with troughing becoming more prominent across the Aleutians, and ridging building north into the eastern Gulf of Alaska and Southeast Alaska by late next week. Showers will be winding down on Wed across portions of Southeast Alaska as a weakening low pressure system pushes inland. Farther west, a low pressure system is expected to cross the Aleutians through the mid to latter part of next week, bringing an increase in showers and perhaps some gusty winds. As this system moves east into the Gulf of Alaska by next weekend, it should spread a round of showers into southern portions of mainland Alaska, and eventually Southeast Alaska as well. The setup farther north across the North Slope an portions of the Interior will be a rather chaotic one, with an arctic upper low initially north of eastern Siberia retreating westward through time, and a rather murky picture of what happens in its wake, but with some potential for additional shortwave energy to affect northern Alaska, keeping some risk for scattered showers and below average temperatures in place. ...Guidance/Predictability Assessment... Model/ensemble guidance showed relatively good consensus early in the extended forecast period, but this degraded quickly at the smaller scales over time, despite some consensus on the described amplifying large scale pattern across the North Pacific next week. Similar to yesterday, 12Z ECMWF/CMC showed perhaps the closest fit with the overall consensus early on, and a blend of these solutions served as a basis for the WPC forecast during days 4-5 (Wed-Thu). After that, weight placed on ensemble means (ECENS and NAEFS) was increased through time. This ensemble-heavy blend later in the forecast period served to smooth differences among the deterministic guidance when it comes to the timing/intensity of individual, smaller-scale systems with low predictability at those tie scales. Ryan 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