"Classic" Migraines...How to Prevent them?

Every now and then I get a severe migraine that is always accompanied bith numbness and tingling in my arms, hands and face. The worst part is the very start of my migraine. I could be driving and in a blink of an eye I lose partial vision...usually peripheral vision. These are warning signs my migraine is on it's way, not a very good warning since this has happened driving my daughter to school. Then I become numb, it's pretty intense in my face, even my tongue. It's so weard! Then my vision usually gets better when the migraine starts. It always lasts between 8-12 hours then just becomes a dull ache through the following day. I live a very healthy lifestyle, I exercise and eat Organic, no dairy and think I am a fairly healthy person. Does anyone have any suggestions on preventing migraines for someone who does not use drugs of any kind over the counter or prescription? I'm always looking for that "Natural" cure. Any advice is greatly appreciated. I am deperate to figure this out and to make thse migraines a thing of the past! Thank you!!