Firefighter Cory Marler tries to pull a reluctant dog to his boat in the flooded Meramec River at Eureka, Mo. Passersby on Thursday spotted two dogs clinging to driftwood in the middle of the river. Sgt. Bryan Parrott of the Missouri Water Patrol, right, comforts the first dog rescued.

Washington ? Government forecasters said Thursday that the floods washing over large parts of the Midwest are just a taste of things to come, with one meteorologist complaining about a jet stream “on steroids.”

Record rainfall and melting snow packs will continue to cause rivers to overflow in large areas of the country, the National Weather Service said.

The greatest flooding danger includes much of the Mississippi River basin, the Ohio River basin, the lower Missouri River basin, Pennsylvania, New Jersey, most of New York, all of New England and portions of the West, including Colorado and Idaho.

“Overall moisture is unprecedented for this time of year over an area that extends over 1,000 miles,” said Doug LeComte, a meteorologist at the government’s Climate Prediction Center.

Joanna Dionne, a meteorologist at the weather service’s Hydrologic Services section, added that “all the ingredients are there for flooding in this broad area and up into the Northeast.”

“American citizens should be on high alert to flood conditions in your communities. Arm yourselves with information about how to stay safe during a flood and do not attempt to drive on flooded roadways,” said Vickie Nadolski, deputy director of the weather service.

Heavy rains have dumped as much as a foot of rain in the Midwest this week, leaving behind more than a dozen deaths. Rivers were cresting above flood stage in Ohio and flooding also was reported in parts of Arkansas, southern Illinois, southern Indiana, Missouri and Kentucky.

On Thursday morning, high water closed the eastbound lanes of Interstate 70 – a major east-west highway – for about 4 miles in central Ohio’s Licking County, the State Highway Patrol said.

LeComte noted that a La Niña, an unusual cooling of the tropical Pacific Ocean has been under way and that often leads to wetter conditions in the U.S. Midwest.

However, he added, “what’s happened in the last few months has not been a typical La Niña; the jet stream’s been on steroids.”

The National Oceanic and Atmospheric Administration said more than 250 communities in a dozen states are experiencing flood conditions this week.

The spring flood forecast said:

¢ Heavy winter snow combined with recent rain indicates parts of Wisconsin and Illinois should see minor to moderate flooding, with as much as a 20 to 30 percent chance of major flooding on some rivers in southern Wisconsin and northern Illinois.

¢ Current snow depth in some areas of upstate New York and New England is more than a foot greater than usual for this time of the year, which increases flood potential in the Connecticut River Valley.