What I meant is it rains along the cold front, then it gets colder behind it without rain, just clouds.
You're basically seeding clouds with the baking soda into the cold conditions where there is moisture but not enough to fall without seeding but it has to be wet for the baking soda to stick and splatter on the roadways so it doesn't blow off until it dries on the roadway where cars and semi's blow a little off at a time in a training effect to the downwind areas.
I will admit, the situation for it to work doesn't come up that often.
Gotta have that big stationary low pressure system and those are far between.