US STOCKS-Wall St jumps for 2nd day, helped by economic optimism

* S&P 500 now positive for 2015 so far

* Jobless claims point to tightening labor market

* Indexes up: Dow 1.8 pct, S&P 1.8, Nasdaq 1.9 pct (Updates to later afternoon)

By Caroline Valetkevitch

NEW YORK, Jan 8 (Reuters) - U.S. stocks jumped more than 1 percent for a second day in afternoon trading on Thursday, lifted by expectations the U.S. economy will continue to accelerate.

Initial claims for state unemployment benefits were slightly above expectations but slipped from the prior week, pointing to a firming labor market just ahead of Friday's key monthly payrolls report.

The advance was broad, with the materials, energy and technology sectors each up more than 2 percent, leading the day's gains.

Stocks on Wednesday had snapped a five-day losing streak after strong private sector jobs data and as minutes from the most recent Federal Reserve meeting reassured investors the bank was in no hurry to start raising interest rates.

The S&P 500 is now on track for a gain of about 3 percent for the last two sessions after losing 4.2 percent in the previous five sessions. The index is in positive territory for the year and back above its 50-day average, a technical support level it fell below on Monday.

"We got some decent data, and this market's got a lot of legs," said Uri Landesman, president of Platinum Partners in New (KOSDAQ: 160550.KQ - news) York.

"There's definitely an increase in discretionary spending" as the result of lower gasoline prices.

Also boosting sentiment, optimism increased that the European Central Bank will take more aggressive action following recent weak data.

The Dow Jones industrial average rose 314.36 points, or 1.79 percent, to 17,898.88, the S&P 500 gained 36.33 points, or 1.79 percent, to 2,062.23 and the Nasdaq Composite added 85.84 points, or 1.85 percent, to 4,736.31.

Biotechs were among the most active shares, recording some of their biggest one-day moves on the back of strong drug study results.

Bind Therapeutics (NasdaqGS: BIND - news) shares surged 59.3 percent after the company said it enrolled its first patient in a mid-stage trial for its lung cancer drug.

Oil's free-fall and global economic weakness were partly behind the recent selloff in stocks. Signs that oil prices may be stabilizing have boosted investor sentiment, although market analysts were still not ready to say prices had found a floor.

U.S. crude oil ended higher for a second day, but it remains below $50 a barrel, settling at $48.79 on Thursday.

Advancing issues outnumbered declining ones on the NYSE by 2,351 to 720, for a 3.27-to-1 ratio; on the Nasdaq, 2,021 issues rose and 716 fell for a 2.82-to-1 ratio. (Additional reporting by Charles Mikolajczak; Editing by Bernadette Baum and Nick Zieminski)