Three Possible Conditions, Checked in Update, Print Condition Only On Condition Change

I know that title was a mouthful. I am using a terrain gradient script, and in order to ensure that it is working correctly I am logging out whether the character is going uphill, downhill, or on flat terrain, during update, but doing so logs that same message over and over. What I want is for it to log only once on gradient change.

Normally you would use a bool and this would be pretty simple, but my problem here is that there are three conditions, and they are each met by a range of values, which is complicating things for me.

Here's what I've tried that isn't working:

bool GradientChange = true;

     if (angle > steepGradient)
     {
         if(GradientChange == false)
         {
             Debug.Log("going uphill");
             GradientChange = true;
         } 
     }
     else if( angle < -steepGradient)
     {
         if (GradientChange)
         {
             Debug.Log("going downhill");
             GradientChange = false;
         }
     }
     else
     {
         if (GradientChange == false)
         {
             Debug.Log("on roughly flat terrain");
             GradientChange = true;
         }
     }