Learn French: Il y a beaucoup de neige devant le chalet. - There is a lot of snow in front of the cabin.

After expressions of quantity like beaucoup (a lot), you use a simple de (or d'). You drop the definite article (le, la, or les) that usually comes before the noun. So, it is always beaucoup de, never beaucoup de la.

Why use devant here instead of avant?

Devant describes a physical location ("in front of" the cabin). Avant is used to talk about time ("before" an event). Since we are talking about physical space in this sentence, devant is the correct word.

Since neige is feminine, does il y a ever change to match gender or plural?

No, il y a is a fixed expression that means both "there is" and "there are." It never changes form, regardless of whether the noun that follows is masculine, feminine, singular, or plural.