* Heavy rain and snow expected this week
* Drier next week but temperatures below average
* Corn seedings already slowest on record
By Sam Nelson
CHICAGO, April 30 Heavy rainfall and snow across roughly the western two-thirds of the U.S. Midwest and the eastern Plains this week will further slow corn plantings that already are the slowest on record, an agricultural meteorologist said on Tuesday.
"They certainly won't get much done this week. There is a big storm system starting Tuesday that will spread in intensity and coverage by Thursday and linger into the weekend," said Don Keeney, a meteorologist for MDA Weather Services.
Keeney said snow could be expected from Nebraska, eastern Colorado, Kansas into the northern Midwest with up to a foot of snow possible in western Iowa. "Elsewhere they'll receive heavy rains of 2.0 to 3.0 inches or more," he said.
"The area affected is generally from Illinois westward and it will definitely put a halt to any additional planting," Keeney said. Drier weather is expected next week but temperatures will remain below normal, slowing seedings and slowing plant germination and growth.
Rain around the U.S. Midwest kept farmers out of fields last week matching the slowest corn planting pace ever, government data released on Monday showed.
The weather also took a toll on the developing winter wheat crop, which deteriorated to its worst condition for this time of year in 17 years.
The U.S. Department of Agriculture (USDA) said corn planting as of April 28, was 5 percent complete, just 1 percentage point ahead of where farmers were a week ago. The pace was the slowest since 1984, when farmers also had completed just 5 percent of their corn planting.
USDA's weekly crop progress report showed the 5 percent corn planting completion pace as of Sunday was a huge drop from 49 percent during the same week a year ago and down sharply from the 31 percent five-year average seeding pace.
Analysts had predicted corn planting to be 9 percent finished, according to the average of 13 estimates in a Reuters poll that ranged from 7 to 11 percent.
Prior to USDA's planting report, corn traders on Monday had expected a slow planting place and bid Chicago Board of Trade (CBOT) corn futures up their daily trading limit of 40 cents per bushel or 6 percent higher for their biggest gain since July.
CBOT corn remained firm in early dealings on Tuesday with the new-crop December futures contract up 2 cents per bushel or 0.36 percent at $5.61-1/2 per bushel at 7:03 a.m. CDT (1203 GMT). (Additional reporting by Mark Weinraub in Chicago; Editing by Chizu Nomiyama)