BOULDER, Colo. (USA TODAY) -- Rescue operations and evacuations continued at a frantic pace Saturday as residents of this flood-hammered state dealt with more swamped roads, inundated homes and the dark forecast of more rain to come.
"It is a sinking feeling when you realize that when some people call ... we are not going to be able to get to them," Boulder County Sheriff Joe Pelle said. "But we are making great progress."
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The sun peeked out over the debris-strewn area Saturday morning, providing a brief respite after days of torrential rains that have left at least four people dead and another missing and presumed dead. Thousands of people have fled their homes.
But showers and storms remained in the forecast in Boulder - which normally sees less than 2 inches of rain in all of September but has been deluged by more than 14 inches this week alone, the National Weather Service said.
"We have another disturbance coming through this afternoon, extending into tomorrow, that could bring another 1-3 inches of rain," Scott Enterkin, a weather service meteorologist in Boulder, told USA TODAY. "We don't expect quite the level of intensity we've seen the last few days, but the soil is saturated, so it won't take much to do damage."
The missing woman could become the fifth confirmed death after witnesses saw floodwaters from the Big Thompson River destroy her home in the Cedar Cove area, Larimer County sheriff's spokesman John Schulz said.
"We're sure there are going to be additional homes that have been destroyed, but we won't know that for a while," Schulz said. "I expect that we're going to continue to receive reports of confirmed missing and confirmed fatalities throughout the next several days."
Many of those driven from their homes may not be able to return for weeks. Early Saturday, National Guard helicopters evacuated hundreds of residents from Jamestown, a mountain town northwest of Boulder.
"Essentially, what they were threatening us with is, 'If you stay here, you may be here for a month,' " 79-year-old Dean Hollenbaugh, who was evacuated by Chinook helicopter from Jamestown, told the Associated Press.
"We are not going to force anyone from their home," Pelle said Saturday, but said that "if they don't come today, we want people to know that we may not be able to get them tomorrow."
Pelle lauded federal emergency officials for their quick response, providing material and personnel on the ground. A day earlier, President Obama declared an emergency for three counties in Colorado, and ordered federal aid to supplement state and local response efforts.
Federal Emergency Management Agency Administrator Craig Fugate said a FEMA assistance team was coordinating with state and local officials. The U.S. Transportation Department said it would immediately provide $5 million in emergency relief funds to help Colorado cover the costs of repairing roads and bridges.
Flood warnings remained in effect Saturday morning from Denver to the Wyoming border. Parts of New Mexico and Texas also were dealing with torrential rains, flooding and evacuations.
Pelle said more than 170 people remained unaccounted for in the Boulder area, but he said they were not considered missing; they have yet to contact family members.
About 15 miles north of Boulder, the Colorado National Guard began evacuating 2,500 residents of Lyons at daybreak Friday.
"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 fiancée to evacuate their home in Lyons after a nearby river began to overflow into the street.
Pelle said he expects the number of those unaccounted for - and the death toll - to rise, because most of the western part of the county remained 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."
Flooding closed Interstate 25, the state's main north-south highway, north of Denver to the Wyoming border. In neighboring Weld County, where more acres of farmland have been turned into lakes and more than 140 roads have been closed, Commissioner Bill Garcia called the flooding an "unprecedented event," The Greeley Tribune reported.
Colorado Gov. John Hickenlooper said the state has lost "a great deal of infrastructure,'' although an exact assessment over flood damage could take weeks.