Reality is, wind tunnels, thermals, etc., are very hard to predict simply because air is something we cannot see, and there are so many variables to consider such as the shape of the terrain, temperature, wind speed, time of day, and elevation. A prevailing wind blowing over a ridge or hill puts pressure on the air on the leeward side. This also creates a line of friction that pulls air upward and creates a circulation that pushes air up the leeward slope. I firmly believe there has to be a strong wind to create this effect. Also, a strong prevailing wind is usually not constant. The wind speed is usually rising and falling. A day with sun shine, thermals do play a role of rapid rising of air parcels closer to the 1/3 elevation line. A day with no sun=no thermals. Any rising air on a sunless day is more likely dependent on strong enough wind to create enough friction to move that air upward. This is all my opinion on what I have researched on my own so far on this sort of topic.
The cave you fear hides the treasure you seek!!!