"It will be windy this afternoon."
Here, the sentence assumes "future" or "will happen" tense. In this case, 会 is used here.
可以 is used when specifying capability of the subject. For instance
which means "I can write Chinese". As an alternative for the translation, 可能 is used to indicate possibility of the event. So another way to express the English sentence is
No you are absolutely wrong. 會/会 is capability. 可以 is permission.