You can set a condition to not trigger the alert until it has existing for X period of time. (See screenshot below.)
As a side note- our UX research team is looking at some interesting ideas as it relates to alerting. Would you perhaps be interested in spending 30-60 minutes checking it out and giving us your thoughts?
OK... I guess that puts me on the D'OH ! list for today. Completely overlooked the obvious. I was trying to complicate the simple.
Thanks for bringing me back to reality.