Glad to hear you two are alright. Even the smallest of tornadoes (EF-0) are violent storms. Certain atmospheric conditions in mountainous terrain will cause the formation of atmospheric vortexes (vortex) more commonly called a "rotor". I believe these conditions generate wind shear. Also in order to create convection in the atmosphere you need only a 1 degree difference in temperature, warmer at lower altitudes than at higher altitudes. Of course the greater the temperature gradient the greater the convection. Add a little wind with uplift from terrain and you have a storm.

http://en.wikipedia.org/wiki/Atmospheric_turbulence

Welcome to the wacky world of aero/hydro dynamics.