Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 800 PM EDT Fri Sep 16 2022 Valid 12Z Wed Sep 21 2022 - 12Z Sun Sep 25 2022 ...Guidance/Predictability Assessment... There is good model consensus with the historical low tracking through the Alaska Mainland in the short-term and the start of the extended period. However, solutions begin to diverge Monday with as the next low approaches the region, particularly the GFS. It was previously noted that it favors a position more south and slower than those of the ECWMF, CMC and the ensemble means. The latest run of the GFS is following suit. A strong ridge is progged to be centered over the eastern Gulf of Alaska and the western part of the state, and with this in place, differences in the timing, location and strengthen of the next low heading toward western Alaska (Tuesday-Wednesday) within the CMC and ECWMF solutions. The CMC and ECWMF were the preferred solutions and so held more weighting of the WPC multi-model and ensemble means blend for the WPC fronts and pressure products. ...Pattern Overview and Weather/Hazards Highlights... The lingering effects of the remnants of Merbok will remain over the Chukchi Sea for the beginning of the extended period, with upslope rains into the western Brooks Range and along the Arctic coast and strong winds. Meanwhile a second developing low will track almost due north across the AKPEN into Bristol Bay and Southwest Alaska by Monday night. This will lead to gap wind and barrier jet impacts further east across Southcentral and the north Gulf Coast. This includes Turnagain Arm winds turning into Anchorage on Tuesday as the low lifts north. Much of the southern Coast and northern portions of the Panhandle will have moderate to heavy rains with strong southerly flow, especially for the coastal mountains. Each day could see 1 to 4+ inches of rain in this pattern. On Tuesday afternoon a strong low (through not nearly as strong as Merbok's remnants) will emerge off of the Kamchatka Peninsula. Its leading front will track eastward along the Aleutian Chain and into the AKPEN by Wednesday afternoon. From there there are significant model differences on how quickly secondary triple-point lows form east of the low. This will determine how quickly the weather deteriorates over the Gulf on Thursday. Very unsettled weather can be expected near the AKPEN and adjacent waters late week. Parts of the Interior will settle and have calm weather by later in the week. Campbell/Wegman Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Tue-Fri, Sep 20-Sep 23. - High winds across portions of mainland Alaska and the Aleutians, Thu-Fri, Sep 22-Sep 23. 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