CHICAGO (Dow Jones)--Chicago Board of Trade corn futures ended higher Thursday as traders covered short positions ahead of Friday's government reports.

September corn ended up 4 cents to $3.09 1/2 per bushel, December corn was up 5 1/2 cents to $3.15 1/4 and March corn was up 5 1/2 cents to $3.28 3/4.

After failing to take out contract lows and $3 early in the week, the market is looking stronger technically, traders said. Short covering was the dominant theme Thursday.

"We've been able to get back up above levels from late last week and make some new weekly highs, so I think most of the price action today is finally a reaction to the weaker dollar and prereport jitters," said Mike Zuzolo, president of Global Commodity Analytics and Consulting.

One trader said a neutral crop production report on Friday morning should give the market the green light to move higher. The market appears to be moving above a trend line in the December contract dating to June highs, he said.

However, expectations of a large crop remain strong as weather forecasts are benign into late September, with no frost threat in sight. The crop needs a late frost to reach its full potential, which most analysts say is huge.

The U.S. Department of Agriculture will release crop production and supply and demand estimates Friday at 8:30 a.m. EDT. The trade is expecting the USDA to increase projected output and, as a result, new crop ending stocks.

But analysts note that private firm Lanworth, which bases its projections in part on satellite imagery, has given traders pause by projection a final yield below 154 bushels per acre. Virtually all other analysts expect the yield to be above 160 bushels.

Outside markets were seen as supportive Thursday, with the dollar lower and crude oil higher. Funds bought an estimated 5,000 corn contracts Thursday.

Also Friday morning, the USDA will release weekly export sales numbers.

CBOT oats futures ended higher. September oats were up 3 3/4 cents to $1.95 1/4 per bushel and December oats ended up 3 3/4 cents to $2.07 1/4.

Ethanol futures were slightly higher. October ethanol was up $0.017 to $1.592 per gallon and November ethanol ended up $0.017 to $1.577.

-By Ian Berry, Dow Jones Newswires; 312-341-5778; ian.berry@dowjones.com