By Jonathan Allen

(Reuters) - The first serious, prolonged storms of the year were brewing on Saturday in the Great Plains, with a growing risk of tornadoes touching down in Arkansas, Louisiana and Texas in the coming days, federal meteorologists said.

A separate storm system sent at least one tornado tearing through coastal North Carolina overnight on Friday. Dozens of homes in Beaufort County collapsed, at least 16 people were hurt and thousands lost electricity, a county official said.

Rescue teams in the county spent the night and early Saturday morning "tearing people's houses apart where their house had collapsed around them," John Pack, the county's director of emergency services, said in a phone interview.

Some 150 homes were damaged or destroyed by winds in excess of 100 miles an hour (160 km an hour), he said, and three people were taken to the trauma center at Greenville Memorial Hospital in South Carolina. Their injuries were serious but not life-threatening, he said.

About 2,500 residents were likely to remain without electricity for at least a couple more days while workers cleared downed trees and repaired power lines, Pack said.

That storm has since moved out to sea, but a new severe storm system is gaining strength in the Great Plains where large hail and damaging winds were expected on Saturday, meteorologists said.

"We're looking at multiple rounds of severe thunderstorms," said Ariel Cohen, a meteorologist at the federal Storm Prediction Center in Norman, Oklahoma.

The storm system was expected to intensify as it moved eastward on Sunday and Monday, with a moderate risk of strong tornadoes touching down in Louisiana, Arkansas, Texas and the lower Mississippi Valley, Cohen said.

The American Red Cross said it had shelters on standby in the affected states to house any people whose homes might be damaged in the storms.

Only 109 tornadoes have been reported in the United States this year through Thursday, less than a quarter of the yearly average of 451 for the same period, according to data kept by the Storm Prediction Center.

No tornado deaths have been reported in the United States so far this year, compared with three through April last year, 66 in 2012 and 365 in 2011, according to the center.

(Reporting by Jonathan Allen in New York, Editing by Alex Dobuzinskis and David Gregorio)