Tornadoes Touch Down In Colorado

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Witnesses say that buildings are damaged, trees are down and electricity has been knocked out. It is believed to be an F3 or F4 tornado and the National Weather Service has issued warnings for parts of Weld and Larimer counties, and residents were urged to seek shelter.

F0 through F6 is how tornadoes are categorized and you can see those categories which are determined using the Fujita Scale.

According to SkyFOX, they have video showing overturned vehicles and a spokeswoman for the Weld County Sheriff's Office, Margie Martinez, reports that two semi trucks have rolled over as well.

A FOX 31 photojournalist, Larry Bases, describes the scene, saying, "It's disastrous here."

This started with a report from a trained spotter of a large tornado on the ground at Platteville, and then the report of a tornado near Gilcrest. Then at about 12:00 p.m., a trained spotter reported a large tornado near Windsor.

The storm was moving to the northwest.

Strong winds gusting up to 70 miles an hour and numerous lightning strikes accompanied this storm.

You can see a list of alerts active right now at the National Weather Service website.

Right now the Colorado counties listed under the Tornado watch category are Adams, Broomfield, Douglas, Kiowa, Lincoln, Phillips, Weld, Arapahoe, Cheyenne, Elbert, Kit Carson, Logan, Sedgwick, Yuma, Boulder, Denver, Jefferson, Larimer, Morgan and Washington.

[Update] Reports say one person has died as a result of these tornadoes that have ripped roofs off of buildings, overturned freight rail cars and tractor trailers.

Gov. Bill Ritter declared a state of emergency for Weld County, mobilizing the Colorado National Guard to assist with disaster response.

The authorities are still trying to assess damages and injuries.

"We have every type of injury, broken bones, cuts, bruises, from everything from falling trees to broken glass hitting them," said Jolene Schneider, spokeswoman for the Windsor Fire Department. "Only thing we are trying to figure out now is how many and how severe."

More from CNN with video of the tornado as it hit.