Friday will also see the quarterly rebalancing of the S&P 500 index. - MarketWatch photo illustration/iStockphoto Friday is the first day of spring. It is also the first “triple-witching” options expiration during what has already been a busy year for markets. Investors are bracing for what could be a doozy of a trading session. Most Read from MarketWatch The notional value of contracts due to expire is slightly lower than the record amount that rolled off in December. Friday’s expiration tally is abo ...