What are the penalties for a minor with simple possession of marijuana?

Possession is only a misdemeanor in the US. At worst, you'll get a fine.

Unless you have multiple ounces, which I forgot the exact amount, then you will get a felony charge, and that's prison time. I think you'll get a felony charge because the court will just assume that's intent to deal, which is why is you have a scale on you, that's also a felony charge.