It is legal to hunt small game during the rifle season. You have to use a shotgun with shot #4 or smaller. Personally I wouldn't be out there for safety reasons alone. But, if you insist, you MUST wear hunter orange just like you are deer hunting. If you can find a conservation area that is closed to rifle hunting it would be a wise choice. There are also plenty of other areas close to the St.Louis region that are better tan MTNF.

As far as weather goes...
Good luck on figuring it out. I can't. The last few years have been pretty crazy. Expect cold to fridgid and maybe a few days in the high 70's. Also bring rain gear because MO is known for wet fall seasons.

Hope I helped.

Rich