How much do you like this girl?
If you really like her, you could take a blank face deck - write names of all the guys in your school...have ONE card that has her name on it. Go up to her...and say, I wrote names of people I want to ask to the dance on these cards...but I am not sure who to take. If there are guys in your school with dual gender names like Robin or Morgan you could show a couple...but it's not required. Ask her for her help to randomly take a card to decide who you want to ask...force her name on her...then express how releaved you are that she picked her own name...because, in all honesty...she was always the only girl for you...LITERALLY...and show her that the rest of the cards were names of the guys in your school....if you are worried about the "you were considering going with a guy" concept - then you can write - "Stag" or "Stay home alone"...really, your imagination on what you write is up to you - and the girls personality on what she would find funny/cute.
You could PRODUCE a rose on top of that - that would clinch it.
Don't do snowstorm...really.
AND FOR THE MILLIONTH TIME - Listen to Katie when it comes to any advice on women...she happens to be a pretty and intelligent - and she has chops to boot - so if you listen to anyone that can help you - the women took time to give you a great tip.
In case you missed it - GO BIG OR GO HOME - what you are about to do is a good lesson in life and magic, as you are creating a memory for this girl - how do you want her to remember this in years to come? Make it hard for her to say no...blow her out of the water man...if you had a gun...would you shoot ONE bullet in a fight to the death...or ALL of them...don't use the fact you are freshman to only shoot one bullet...it's not lame - trust me...or Katie!
Good luck mate - I want to hear about how it turns out.