My frozen wasteland has bald spots. How do I make it not bald?

roughly half of my entire custom frozen wasteland dimension (basically just copy pasted frozen plains and frozen taiga and edited them a tad) is snowless. This is a bad thing because it is supposed to be a frozen wasteland. How would I go about guaranteeing it's covered in snow? The temp modifier is frozen on both of them. Sidenote, despite precipitation being enabled, there's no snow when I use the weather command to make it rain..