I remember there was a day maybe ten or twelve years ago that looked like a historic NE outbreak. I seem to recall the SPC had a 10 or 15% hatched tornado for us in the outlook. Shear was awesome, instability was sufficient, strong trigger....but we overlooked the lapse rates, which were awful. Lo and behold, whatever updrafts tried to go up were feeble and just got blown over by the shear. Brutal bust, so painful I can't even recall when that day was.
Edit: found it. June 6, 2010. 80 kt jet, 60 kt bulk shear, raging llj, 45% hatched wind, 10% tornado. Epic epic bust.