La Nina to linger to spring: U.S. CPC ORLANDO, Florida (Reuters) - La Nina, the weather phenomenon widely blamed for withering drought in the southwestern United States and South America, may last longer than expected, into the Northern Hemisphere spring, the U.S. Climate Prediction Center warned on Thursday. "The latest observations ... suggest that La Nina will be of weak-to-moderate strength this winter, and will continue thereafter as a weak event until it likely dissipates sometime between March and May," the CPC said. The CPC's latest monthly update is the first to raise the prospect of La Nina persisting well into the spring. Forecasters had expected the phenomenon, which has already raised concerns in grain, oilseed, sugar and coffee markets, to be present during the Northern Hemisphere winter. In its previous assessment in December, the CPC, an office under the National Oceanic Atmospheric Administration (NOAA), said La Nina's strength would weaken at the onset of spring. La Nina, which can last for several years, is the opposite number of the more infamous El Nino anomaly and is caused by an abnormal cooling of waters in the equatorial Pacific Ocean. El Nino leads to warming of those waters. Both wreak havoc in weather patterns from South and North America to India and possibly even Africa. The CPC also warned on Thursday that La Nina will mean "drier-than-average conditions are more likely across the southern tier of the U.S." An extended dry period could cause problems for farmers from the Carolinas to Kansas planning for sowing in the spring, anlaysts said. Kansas, which recently was hit by storms, should have enough moisture, but a severe drought in Oklahoma and Texas has already drained the soil there, Sterling Smith, senior analyst at Country Hedging Inc said. That could mean another drought for cotton farmers in Texas, whose crops were hit last year by a La Nina-inspired once-in-a-century drought. Texas is the biggest cotton growing state in the country. "It could worsen the possibility of a dry spell in Texas," said Smith. Fears about La Nina's impact were already heightened before the CPC's outlook. The 2011/12 corn crop of Argentina, the world's No. 2 supplier, will be smaller than initially forecast due to dry weather linked to La Nina although output should still hit a record. In leading palm grower/exporter Malaysia, severe monsoon rains from La Nina could disrupt harvesting and boost palm oil prices. Rains in the December to March period are also posing a threat to the coffee crop in Colombia, the world's top source of high quality beans. La Nina lasting until the Northern Hemisphere spring would also bring it to the cusp of the start of the annual Atlantic hurricane season on June 1. In the last two years when La Nina was present, more storms formed in the Atlantic Ocean, but most veered away from the U.S. mainland, with the exception of Hurricane Irene and the severe damage it caused in states from New Jersey to Vermont. Reporting By Rene Pastor; Editing by David Gregorio