A quarter-mile-wide tornado cut a swath across mainly open country in southeastern Wyoming, damaging homes, derailing empty train cars and leaving one person with minor injuries, officials said.
The twister was part of a powerful storm system that rolled through parts of Colorado and Wyoming Thursday afternoon and evening, packing heavy rains, high winds and hail. The storms followed a round of nasty late spring weather that pummeled the region Wednesday.
Thursday's tornado in a sparsely populated area near Wheatland, Wyo., left five structures heavily damaged, and 10 to 12 other structures had lesser damage, said Kelly Ruiz of the Wyoming Office of Homeland Security. One of the destroyed homes was vacant, said local radio station owner Kent Smith, speaking for the Platte County Sheriff's Office.
One person was treated at a hospital for a cut on the head, Smith said.
National Weather Service meteorologist Richard Emanuel said the tornado was one-quarter mile wide and stayed on the ground for much of its 20-mile path from west of Wheatland to northeast of Chugwater. The area is about 60 miles north of Cheyenne.
"It stayed pretty much over open country," Emanuel said. "It didn't hit any towns or cities."
A twister of that size and duration on the ground was unusual for Wyoming, he said.
Some power lines also were downed, Ruiz said.
Hail the size of golf balls was reported in the Wheatland area, and 2-inch hail was reported in Laramie, National Weather Service meteorologist Tim Trudel said.
Elbert County officials reported damage to eight houses, including two that were missing roofs and others with broken windows. They also received a report of one minor injury, county emergency management spokeswoman Kara Gerczynski said. Meanwhile 2.5-inch hail was reported in El Paso County near Peterson Air Force Base.
Bernie Meier, a National Weather Service meteorologist stationed in Boulder, said a storm that crossed into the state from Wyoming hit the Greeley area with golf ball sized hail. Though he had no immediate reports of damage, he said it was likely given the size of the hail.
The storms were winding down late Thursday and forecasters said drier weather was expected Friday.
Thursday's storms came as Colorado businesses including a grocery store were cleaning up the mess left after a storm system brought about five tornadoes, hail up to 8 inches deep and heavy rain Wednesday night. No serious damage was reported from the tornadoes Wednesday, but snowplows were called out in Douglas County to clear hail, and firefighters in Colorado Springs rescued about 40 people from flooded cars and homes.
Insurers reported receiving several hundred home and automobile claims in Colorado before the new wave of storms arrived Thursday evening.
The rain provided some help to firefighters who fully contained a 227-acre wildfire in northern Colorado, but the weather initially hurt efforts to control a 6,000-acre blaze in Wyoming's Medicine Bow National Forest.
Storms passed close to the Wyoming fire but mostly brought gusty winds that fanned the flames. Rain and hail fell later but didn't make a significant difference, said fire spokeswoman Beth Hermanson.
Kyle Fredin, a meteorologist for the National Weather Service in Denver, said the beginning of June is the peak time for such severe weather in Colorado. Most of the state has been experiencing moderate-to-extreme drought conditions.
"It's game-on for this type of thing," he said.
Copyright 2012 The Associated Press.