US STOCKS-Futures higher as positive momentum persists
* Wall St rises again, but volatility expected
* Pfizer, Novartis may bid for Onyx: sources
* Zynga shares jump in premarket after hiring new CEO
* Futures up: Dow 32 pts, S&P 5.2 pts, Nasdaq 8.25 pts
By Ryan Vlastelica
NEW YORK, July 2 (Reuters) - U.S. stock index futures rose modestly on Tuesday, indicating positive market momentum would continue as investors remain more comfortable with the economic outlook.
* Equities surged in the first half of the year, hitting a series of record highs before pulling back dramatically in June on concerns over when the U.S. Federal Reserve would begin reining in its stimulus program. The policy is widely credited with fueling 2013's gains.
* Comments last week from Fed officials that the end to the program wasn't imminent helped equities stabilize after the decline, though the S&P 500 remains more than 3 percent below from its record closing high.
* Investors will watch the latest economic data, including May factory orders, which is seen rising 2 percent, twice the rate of the previous month. The report is due at 10 a.m. EDT (1400 GMT)
* Data on May durable goods and the Institute for Supply Management's New York index are also on tap on Tuesday.
* Wall Street has had a confused relationship with data of late, as bullish reports sparked declines on concerns any sign of a strong economy will cause the Fed to tighten its bond- buying program. However, last week's comments from Fed officials reassured investors.
* Still, stocks closed higher on Monday on strong manufacturing and construction data.
* S&P 500 futures rose 5.2 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures added 32 points, and Nasdaq 100 futures were up 8.25 points.
* Shares ended on Monday well off session highs. The S&P lost more than half of its gains, a sign of investor caution. More volatility is expected as the economy eventually transitions to a no-stimulus environment.
* In corporate news, sources said Pfizer Inc and Novartis AG may make preliminary bids for Onyx Pharmaceuticals Inc. On Sunday, Onyx turned down a roughly $10 billion offer from Amgen Inc.
* Zynga Inc rose 3.2 percent to $3.23 in premarket trading after naming Don Mattrick, the head of Microsoft's Xbox business, as its chief executive.
* Constellation Brands Inc is the only S&P 500 company scheduled to report on Tuesday. Earnings season begins in earnest next week. (Editing by Jeffrey Benkoe)