Sometimes your pathways make the snowballs bigger. Think it's when it starts snowing more.
Finding a dirt spot or using the train or event plaza is helpful. Also having room to see.
Sometime it's best just to let the snowball fall off the cliff or hit a tree.
They can be far apart and too much of a pain. Just go into the train station or a building after. Sometime they are close to the 1st snowball.