Background
The pilot had previously made a flight in the same direction from a remote lake toward rising terrain. On that initial flight, winds were estimated at 7 to 10 knots, and the flight was completed without incident.
Accident Flight
During the subsequent takeoff from the same lake, the pilot reported that soon after departure, the airplane encountered winds estimated at 40 knots. The pilot stated that an associated downdraft prevented the airplane from climbing away from the rising terrain ahead.
Pilot Report
According to the pilot, in response to the inability to gain altitude over the terrain, he elected to land the airplane in the tundra rather than continue into higher terrain. No further details about the landing or aircraft condition were provided.
Conclusion
The pilot's account indicates the decision to land was based on the sudden change in wind conditions and the downdraft, which made continued flight toward higher terrain infeasible.