Raising the Bar

After my most recent marathon, the urge to take on bigger challenges grew considerably. I am hardly a dominant marathon runner and I certain can still get much faster, but I didn't feel particular challenged nor was there any uncertainty as to whether or not not I would finish.  I have already signed up to run the Greenland 50K on May 4, 2013 but the additional six miles seems to be a fairly modest step up.  I really want to go out and tackle a 50 mile or 100 mile run.  These would be a whole new ballgame and would once again bring the uncertainty as to whether or not not I would finish back into the equation.  Fifty miles sounds more pleasant to me but I'd like to knock of 100 miles at some point even if it does sound like a death march.  The question now is how do I get ready for something like this without over-training and/or hurting myself and what event should I pick.  Colorado has several options but most of them sound kind of brutal but I'm always a bit reluctant to leave my normal training environment for I'm found that heat and humidity sometimes hit me harder than altitude.  The Leadville 100 would be awesome eventually.  I think that the Leadville 50, Run Rabbit Run 50 or Bear Chase 50 are the races I will target in 2013 (one not all three).  We'll see how it goes.