I don't think it has anything to do with what's near the verb. It's all to do with what the speaker has in mind as the sentence subject. The verb agrees with the subject. Where people go wrong on this issue is in thinking of the grammatical subject rather than the logical subject. This is not to do with grammar but with meaning.
You could argue reasonably that the writer was indeed thinking of avalanche as the logical subject, and that there was an error in the writing or editing process, but I really think that's unlikely.