Changing weight of sections for mobile (closed)

Closing this thread because I double-posted. Use this thread instead:

http://groups.drupal.org/node/266873#comment-865743

I'm moving a site to Drupal + Omega.

On the existing site, a sidebar displays on the left in the desktop version, but at the bottom in the mobile version.

In the Omega version I have put the contact us box in the "sidebar second" region of the content section/zone, which has a weight of 3. This works for mobile (putting it at the bottom) but in the desktop views it is on the right.

How can I accomplish the original design of the sidebar second displaying in the bottom on mobile, but on the left in desktop?