How are Winds Aloft used if an altitude value of less that the routes terrain altitude is used for part of a flight?

When planning a route, you will get the best winds aloft corrections and fuel burn if you use an altitude for your route that is higher than the terrain for the entire route of flight.  

ForeFlight does not allow for step climbs in the NavLog, so if you intend to use multiple altitudes for a route of flight, it may be best to plan the route in multiple segments.  

If you plan a route with an altitude that is less that the altitude of the terrain for a portion of the flight, then the winds aloft corrections may not be as accurate due to the altitude conflict with terrain.