My vague (probably flawed) interpretation is:
Contracts are being exercised, large money hedgers are switching to the next contract so they have to liquidate their existing contracts. Therefore, it creates some false type of moves.. for example, large money shorts covering their positions by buying. This causes the market is go up, but remember this is exiting a position and not meant to imply an uptrend. Therefore, the upmove usually has no followthrough when the lemming traders pile in. Therefore, one should expect a decent sized ranged type of day with minimal followthrough. Rallies get sold into, dips get bought.
fwiw, this gap up today is not optimal for longs to start building positions either - so it would not surprise me to see today's rally fail today or early tommorrow.