Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 722 PM EDT Fri May 12 2023 Valid 12Z Tue May 16 2023 - 12Z Sat May 20 2023 ...Spring warming to advance eastern Interior snowmelt runoff and river ice breakup threats into next week†...Guidance Evaluation/Predictability Assessment... Recent model run to run continuity and forecast spread have increasingly become worse than normal through short and especially medium range time scales. The 18 UTC GFS has trended toward the 12 UTC ECMWF in some aspects, but this may be a red herring and suspect future runs with again diverge in this complex pattern sensitive to initialization and system interactions. Without a clearer signal to support the embedded features and trends of the latest models, suggest usage of more compatible 12 UTC GEFS/ECMWF ensemble means blend to best maintain WPC product continuity along with hazards and messaging. These composites tend to mitigate small-mid scale variances consistent with predictability. Applied manual edits to ensure sufficient surface low pressure center depths and wind speeds as supported aloft but otherwise muted by the blending process and forecast spread. ...Overview and Weather/Hazard Highlights... Expect a warming/drying trend over Southeast Alaska next week with ridging at the surface and aloft settling over the region. Upper ridging and warmer temperatures are also forecast farther north into at least the eastern Interior/North Slope by early next next week, which even as temporary, could broadly increase the rate of snowmelt runoff and river ice breakup and lead to flooding threats. Meanwhile, the slow advance and uncertain splitting of supporting upper trough energies will act to bring additional low pressure systems across the eastern Bering Sea and western/southwestrn Alaska and also downstream with modest lead triple point developments, mainly into the northwestern/northern Gulf of Alaska. This combination will spread moderate precipitation from the Alaska Peninsula and Kodiak Island to Southcentral, but also well northward, especially across western Alaska. Guidance does not show excessive amounts, but has trended upward, especially for western Alaska and down into the Kenai Peninsula and vicinity. The northward feed of moisture and Gulf system energies in a channeled conduit into the mainland between the Bering system and the amplified downstream upper ridge may prove efficient, especially for favored coastal terrain. Expect scattered precipitation across the Interior next week as system energies work inland. Schichtel Hazards: - Much above normal temperatures across eastern Interior Alaska, Mon-Tue, May 15-May 16. 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