It snowed last week and I noticed that, when my car was stationary, snow built up on the windshield, but above about 10 mph (4.5 m/s, if SI units are required here), the snow didn't stick. I'm wondering what accounts for the difference. My first thought was that the extra kinetic energy of my car's motion would be enough to sublimate falling snowflakes. After a few mathematical missteps, however, I determined that my car would have to be going about a thousand times faster than I was willing to drive it to get the required amount of energy. That is to say, this was too little energy by a factor of about a million. Which leaves me at somewhat of a loss. I wouldn't be at all surprised if the temperature of my windshield plays a role, but I can't see how my car moving forward would affect that equation. The only other thought that comes to mind is that the air my car pushes through might exert some pressure on an incoming snowflake, such that the snowflake isn't able to land. But the physics I've taken was a little light on fluid mechanics, so I'm not sure how to proceed from there. Any help you folks can provide would be greatly appreciated. I don't even require anyone to spell out the answer for me; if I can be pointed in the right direction, I'll try to work out the problem myself. Some relevant factoids: Wiki says a typical snowflake is 1019 water molecules, which would give it a mass of about 3x10-7 kg, and I estimated that a snowflake's terminal velocity is somewhere around 1 m/s from this paper. Thanks.