I'm guessing the difference in temperature from the light and dark side causes a concurrent difference in gas pressures. The denser, cooler "air" rushes to fill the pressure differential of the warmer, thinner "air".
The wind velocity at the surface is vanishingly small (under 1 meter per second, less than 2 mph), and velocity doesn’t rise until miles of altitude (not Earthly at all); for Venus’ atmosphere is also opaque to sunlight, to the extent that zero sunlight reaches the surface; and the axial rotation of the planet is very slow, and retrograde.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html