CNBC's Pisani: "Unusual Gain" in S&P

Very unusual first half hour of trading, with S&P 500 up nearly 10 points at one point, blowing through the resistance at 1415 or so.

A 10 point gain on no news is unusual; most likely explanation is this is related to quadruple witching expiration (this is the expiration of options and futures on indexes, and options and futures on individual stocks, which happens four times a year and often causes volatility).

It's likely the Wall Street dealer community is long calls, so they would have a vested interest keeping the markets up, at least through the open tomorrow.