US STOCKS-Wall St gains for second day; eyes on payroll data Fri
* Volatility expected ahead of Friday's payroll report
* Fed's Dudley to speak about national economic conditions
* Ford Motor shares rise after June car sales data
* Indexes up: Dow 0.3 pct, S&P 0.3 pct, Nasdaq 0.2 pct
(Updates to market open, adds economic data)
NEW YORK, July 2 (Reuters) - U.S. stocks rose for a second straight day on Tuesday, with market momentum remaining strong as investors grew more optimistic about the economic outlook.
Trading will likely be thin this week, with U.S. markets closing early on Wednesday and all of Thursday for the Fourth of July holiday. This lower volume could signify greater volatility, especially with the release of the nonfarm payroll report on Friday.
"While all eyes are on the payroll report, markets are holding up as investors are holding out on the hope that we'll see higher highs," said Todd Schoenberger, managing partner at LandColt Capital in New York. "We'll mostly tread water until Friday, but people aren't selling their gains."
Wall Street has shown signs of positive momentum recently, with investors becoming more optimistic about the economic outlook since Federal Reserve officials signaled the central bank's bond-buying stimulus policy wasn't ending imminently.
Adding to the positive tone, Ford Motor Co rose 1.4 percent to $15.96 after reporting "very encouraging" growth of 13.4 percent in June car sales.
The Dow Jones industrial average was up 42.60 points, or 0.28 percent, at 15,017.56. The Standard & Poor's 500 Index was up 4.23 points, or 0.26 percent, at 1,619.19. The Nasdaq Composite Index was up 5.62 points, or 0.16 percent, at 3,440.11.
Equities surged in the first half of the year, hitting record highs before pulling back dramatically in June, on concerns the Fed would begin reining in its stimulus measures, which have helped fuel this year's gains.
While markets have stabilized after a recent slump, the S&P 500 remains more than 3 percent below its record closing high.
William Dudley, president of the New York Fed, will speak at 12:30 p.m. (1630 GMT) about national economic conditions. His comments will be closely scrutinized for clues on when the Fed will begin to scale back its quantitative easing.
Data showed May factory orders rose 2.1 percent, above expectations for a 2 percent rise. Earlier in the day, the Institute for Supply Management's New York index came in at 578.1, compared with 579.6 in the previous month.
Wall Street has shown an ambiguous attitude toward U.S. data over the past six weeks, as positive reports sparked declines as investors fretted that signs of economic strength would prompt the Fed to prematurely scale back its bond-buying program.
The Labor Department will report June non-farm payrolls on Friday, and economists have forecast an increase of 165,000 jobs.
The stock market will have a shortened session Wednesday and U.S. financial markets will be closed for Independence Day on Thursday.
In corporate news, alcoholic beverage company Constellation Brands Inc fell 0.8 percent to $52.67 after its first-quarter earnings and revenue missed expectations.
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.
Onyx jumped 1.6 percent to $133.40, extending its rally of more than 50 percent in Monday's session.
Zynga Inc rose 10 percent to $3.38 after naming Don Mattrick, the head of Microsoft's Xbox business, its chief executive.
(Editing by Bernadette Baum)