Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 340 PM EDT Fri Mar 30 2018 Valid 12Z Tue Apr 03 2018 - 12Z Sat Apr 07 2018 ...Pattern Overview and Guidance/Uncertainty Assessment... A deep/cooling mid-upper level troughing centered over eastern Alaska early next week is expect to steadily retrograde westward as a closed trough/low all next week to eventually surplant a current and highly amplified Bering Sea ridge aloft. This transition seems well supoprted by guidance, but surface system reflections mainly offshore on the periphery of this flow offer below average predictability over time. Recent GFS/ECMWF deterministic model runs have been well clustered with ensembles Day 4/Tuesday so a composite guidance blend seems reasonable. Forecast spread increases quickly thereafter though with the models in particluar struggling with run to run continuity of mid-upper level shortwave trough progressions/interactions and especially the associated surface low developments offshore. Accordingly, the WPC Alaskan product suite was primarily derived from a blend of the more compatable 00 UTC GEFS/ECMWF ensemble means days 5-8. This maintains decent WPC continuity. ...Weather Highlights/Threats... Expect a relatively benign threat pattern to continue for much of Alaska next week with mainly modest precipitation potential overall. An exception may be associated with closed low/trough retrogresion and cooling over the southern third of mainland Alaska where there will likely be potential for unsettled wintery weather including some locally enhanced snows despite limited moisture. Otherwise, an uncertain series of lows for the Aleutians and downstream over the Gulf of Alaska should modestly effect the Aleutians, maritime interests, and southern/southeastern Alaskan coastal communities. However, potential may grow through next week with flow retrogression. Schichtel