(New throughout; updates prices, adds quotes, changes byline, changes dateline from previous SINGAPORE/PARIS)

CHICAGO, Feb 20 (Reuters) - Chicago Board of Trade (CBOT) wheat futures rose nearly 4% on Tuesday, rebounding from life-of-contract lows as a softer dollar and the approach of the spring growing season in the northern hemisphere sparked a short-covering rally, analysts said.

CBOT corn and soybeans also firmed but hovered near multi-year lows.

As of 12:54 p.m. CST (1854 GMT), most-active May wheat was up 22 cents at $5.81 per bushel, bouncing after hitting a contract low at $5.53-1/2.

CBOT March corn was up 3-1/2 cents at $4.20 per bushel after dipping to $4.14-3/4, the lowest on a continuous chart of the most-active contract in more than three years. March soybeans were up 5 cents at $11.77-1/4 a bushel but held above a multi-year low set last week.

Ample global grain stocks and weak demand for U.S. supplies have pressured CBOT corn, wheat and soy futures for months, encouraging speculators to build large net short positions in all three markets. But attention is starting to shift to the U.S. growing season and weather risks, at a time of heightened political tensions.

"Geopolitical risks remain elevated, leaving fund managers worried about their big short positions," StoneX chief commodity analyst Arlan Suderman said in a note to clients.

After the U.S. Department of Agriculture (USDA) last week released forecasts that projected rising stockpiles of U.S. grains, "maybe we have reached peak bad news ... maybe we have just pushed the fund shorts as far as we can," said Sterling Smith, director of agricultural research at AgriSompo North America.

Once CBOT March futures contracts enter their delivery phase later this month, Smith said, "we are going to be looking more at the new crop. Funds will not be as inclined, initially, to drive these massive shorts they have into the new crop (months), simply because we have planting risk and weather risk."

On the export front, the USDA confirmed private sales of 155,000 metric tons of new-crop U.S. corn to Japan and 228,000 tons of old-crop U.S. soymeal to the Philippines. (Reporting by Julie Ingwersen; additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; editing by Barbara Lewis)