Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 330 PM EDT Mon Mar 18 2019 Valid 12Z Fri Mar 22 2019 - 12Z Tue Mar 26 2019 ...Weather Highlights/Hazards... Guidance still highlights a stormy weather pattern quite favorable for multiple periods of terrain and coastal convergence enhanced precipitation especially into the southern coast of the Mainland as well into Southwest and northern Southeast Alaska through this medium range period. Moist inflow will continue to wrap around an prolonged and active series of deep Gulf of Alaska surface lows that re-develop and interact as energies work under influence of an amplified mid-upper level mean trough/closed low. Systems will tap atmospheric rivers to produce daily totals averaging several inches with some additional and locally favored multi-day totals of 10+ inches. The airmass quickly loses moisture content farther inland, but continue to expect modest snows inland from southwest Alaska to the western/central Interior to northern Alaska as energy lifts in a channel between a Bering Sea mean mid-upper level trough/low and an Interior Alaska/western Canadian mid-upper level ridge. Relatively dry conditions are expected to persist for much of the east-central Interior under that ridge. Meanwhile, expect stormy conditions for the Bering Sea/Aleutians this period as deep surface lows develop under a mean closed upper low/trough position. Models and ensembles have shown quite a bit of run to run variance recently, lowering forecast confidence in particular solutions. Highly unsettled weather will accordingly work steadily underneath and eastward with system progression through the Aleutians and toward the Alaska Peninsula/southwest Alaska with triple point low transitions downstream of the deep parent lows. ...Guidance Assessment... A composite guidance solution seems reasonable for Friday when forecast spread is relatively low. After consultation with local Alaskan WFOs, the WPC Alaskan Days 5-8 product suite was then mainly derived from ensemble means amid growing uncertainty with emphasis on the ECMWF ensemble mean to maintain best continuity. Schichtel Bullet points from the WPC Days 3-7 Hazards chart can be found at: https://www.wpc.ncep.noaa.gov/threats/threats.php - Heavy precipitation for southern mainland Alaska, Thu-Sat, Mar 21-Mar 23. - Heavy precipitation for the Alaska Panhandle, Sun-Mon, Mar 24-Mar 25. - High winds for southern mainland Alaska and Aleutians, Thu-Fri, Mar 21-Mar 22. - High significant wave heights for coastal southern mainland Alaska, Fri, Mar 22. 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