Is Southwestern Mandarin different from Mandarin? I'm moving in two years to Yunnan. I'm learning Mandarin. But I've read that in Yunnan the official language is "Southwestern Mandarin". 

What's the difference? Will they be able to understand me?
Southwestern Mandarin，西南官话，实则是西南方言

Mandarin，普通话，全国通用

你在任何地方说普通话都可以交流

Southwestern Mandarin只在西南部分地区交流
当然只是语调的部分不同