BOULDER, Colo. — Authorities Friday confirmed a fourth death from widespread flooding that forced fresh evacuations of thousands of residents, as additional rainfall threatened already swollen rivers and creeks along a 150-mile stretch of the state's Front Range.
Boulder County officials also said 80 people remain unaccounted for but are not considered missing; they have yet to contact family members.
Rain continued to fall Friday, and forecasters predicted that local downpours and flooding would persist through the weekend.
About 15 miles north of Boulder, the Colorado National Guard began evacuating 2,000 residents of Lyons — isolated, without power and running water because of flooded roads Thursday — at daybreak, according to the Boulder County sheriff's office. In South Boulder County, 500 residents in Eldorado Springs were also under evacuation orders. County emergency personnel said the Guard was using high-clearance trucks to move Lyons residents to safe areas.
"There's no way out of town. There's no way into town. So, basically, now we're just on an island," said Jason Stillman, 37, who was forced with his fiancee to evacuate their home in Lyons after a nearby river began to overflow into the street.
Flooding closed I-25, the state's main north-south highway, north of Denver to the Wyoming border, among several roads blocked by rising waters.
The National Weather Service had a flood warning for Boulder County through Friday morning. Flood warnings were also issued for the city of Loveland and Big Thompson Canyon, site of the July 1976 flood that killed 143 people. The Big Thompson River was reported over four feet above its flood stage.
Colorado Gov. John Hickenlooper said the state has lost "a great deal of infrastructure,'' although an exact assessment over flood damage could take weeks.
Hickenlooper urged residents near flood areas to remain "exceptionally careful" and stay away from swollen streams and rivers. "People try to walk through what looks like a harmless foot or two of water. You have to realize this is like liquid cement and you can be swept away."
The National Weather Service forecast more rain over portions of Colorado Friday, with up to three inches or more falling in some areas.
After today, "a slow-moving area of low pressure over the Rockies, combined with a moist, southerly flow at all levels of the atmosphere will keep the threat of locally heavy rain and flooding in place into the weekend," says Weather Channel meteorologist Chris Dolce.
In Boulder, officials issued emergency alerts to 8,000 residents along normally tranquil Boulder Creek, urging them to seek shelter elsewhere or move to higher ground. About 4,000 residents along Boulder Canyon faced mandatory evacuation. Officials fear mud and rocks accumulating in Boulder Canyon will clog and cause a sudden surge in water downstream.
Officials planned to publicly release the names of those still unaccounted for. "'Unaccounted for' doesn't mean missing. It means we haven't heard back from them," said county spokesman James Burrus.
Boulder Sheriff Joe Pelle said at a Friday afternoon news conference that he expects the number of unaccounted for -- and the death toll -- to rise, because most of the western part of the county remaind inaccessible.
"The things that worry us are what we don't know," he said. "We don't know how many lives are lost, we don't know about homes lost."
The flood that swept down Boulder Creek was a 1-in-100 year event, the U.S. Geological Survey said Friday. The college town is considered Colorado's 'most at risk' city to flooding because of its proximity to Boulder Creek, which courses through Boulder Canyon into the heart of town, says Weather Underground weather historian Christopher Burt.
With up to a foot of rain falling in some areas, grounds are so saturated that more rain could cause flash floods in some areas, the Federal Emergency Management Agency warned.
Two Maine backpackers hiking Longs Peak were stranded when the weather turned. Suzanne Turell and Connie Yang of York, Maine, last sent a text message shortly after 7:07 a.m. Thursday with their GPS coordinates.
"We need help,'' said Turell, who added that they were at risk for hypothermia because of an ice storm at elevations above 13,400 feet. The cellphone has since gone dead,
Hundreds of residents spent Thursday night at evacuation centers, while thousands remain without power or are isolated by flooded roads. Friday morning, the creek was just under flood stage.
Flooding along the Poudre River prompted Fort Collins officials to "strongly urge"residents in at least four neighborhoods to flee.
The National Weather Service said Windsor, Estes Park, Berthoud and Drake remain at risk for flooding.
Boulder, home to the University of Colorado, was among the hardest hit by the devastating waters. Classes have been canceled until at least Monday, with 25% of the campus buildings water-damaged.
President Obama signed an emergency declaration Thursday night, freeing up federal aid and allowing FEMA to coordinate disaster relief efforts.
Flooding extended all along the Front Range mountains — including in Denver, Colorado Springs, Fort Collins, Greeley and Aurora — as well as scores of small towns and mountain communities.
One person was killed in the collapse of a home in Jamestown, a mountain community isolated by washed out roads, KUSA-TV in Denver reported. Colorado Springs police found a second victim in Fountain Creek -- later identified as 54-year-old Danny Davis.
Friday, searchers found the body of woman swept away Thursday after the vehicle she was in got stuck in water north of Boulder, KUSA said. The driver died after he got out to help her. Neither have been identified.
Boulder was doused with more than 7 inches of rain in 24 hours, shattering the town's 95-year record for rainfall.
Near the town of Lyons, rescuers were kept back when St. Vrain Creek swelled and a dam failed near Pinewood Springs.
"It's just raging, gushing water,'' Lyons resident Carin Gray said. "We're totally isolated.''
Hughes reported from Colorado; Welch reported from Los Angeles. Contributing: USA Today's Doyle Rice and Donna Leinwand Leger and the Associated Press