GRAINS-U.S. wheat futures tumble as rains cross drought-hit Plains

* K.C. wheat leads declines, with May contract down 5 pct

* Soybeans lower on showers in Argentine crop belt

* Corn down on spillover from wheat, long liquidation

(New throughout; updates prices, adds quotes, changes byline, dateline, previous PARIS/SINGAPORE) CHICAGO, March 19 (Reuters) - U.S. wheat futures slid to six-week lows on Monday as much-needed rain and snow fell in dry areas of the southern Plains, pushing most-active K.C. hard red winter wheat futures down more than 5 percent, traders said. Soybean futures sagged as beneficial weekend rains reached dry areas of Argentina's soy belt, and corn followed the weak trend. As of 12:07 p.m. CDT (1707 GMT), Chicago Board of Trade May wheat was down 13-1/2 cents at $4.54-1/4 a bushel while K.C. May wheat was down 26-1/2 cents at $4.73 after dipping to $4.72, its lowest since Feb. 5. CBOT May soybeans were down 24 cents at $10.25-1/2 a bushel and May corn was down 6-3/4 cents at $3.76. Wheat posted the biggest declines on a percentage basis as rain and snow fell in the southern Plains, parts of which have been dry since October. The storm should generate about 1 inch (2.5 cm) of liquid precipitation for northern, central and eastern Kansas, the top U.S. wheat state, said Don Keeney, an agricultural meteorologist with Radiant Solutions. The region's hard red winter wheat is starting to emerge from dormancy and resume spring growth, a phase that ratchets up its need for moisture. "The pattern is expected to revert dry again behind this system, but for now, the current system provides a million-dollar rain for Kansas, buying the crop some time," INTL FCStone chief commodities economist Arlan Suderman said in a note to clients. CBOT corn was lower on spillover pressure from wheat and long liquidation by commodity funds that, in the week to March 13, had built up their biggest net long in CBOT corn since June 2016, according to U.S. Commodity Futures Trading Commission data. CBOT May soybeans dipped to $10.23-1/2, their lowest in about a month, as rains fell in crop areas of Argentina. The showers may have arrived too late to significantly bolster drought-hit soybeans, but "it stops the bleeding," said Tom Fritz, a partner with EFG Group in Chicago. Last week, the Rosario Grains Exchange slashed its estimate of Argentina's soybean crop to 40 million tonnes, from 46.5 million previously, following months of dry weather.

CBOT prices as of 12:09 p.m. CDT (1709 GMT):

Net Pct Volume

Last change change

CBOT wheat WK8 453.75 -14.00 -3.0 76136 CBOT corn CK8 375.75 -7.00 -1.8 173163 CBOT soybeans SK8 1025.25 -24.25 -2.3 96846 CBOT soymeal SMK8 359.60 -13.30 -3.6 71158 CBOT soyoil BOK8 32.03 0.05 0.2 43679

NOTE: CBOT May wheat, corn and soybeans shown in cents per bushel, soymeal in dollars per short ton and soyoil in cents per lb.

(Additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by David Evans and James Dalgleish)