"We're not trying to force anyone from their home. We're not trying to be forceful, but we're trying to be very factual and definitive about the consequences of their decision, and we hope that they will come down," Boulder County Sheriff Joe Pelle said.
Special education teacher Brian Shultz, 38, was torn about leaving his Jamestown home.
"I was thinking about staying. I could have lasted at least a year. I have a lot of training in wilderness survival," he said, adding that he probably had enough beer to last the whole time.
As he sat outside a makeshift shelter at a high school, Shultz floated the idea of walking back into the funky mountain town.
"If we hike back, I would stay there and just live. I'd rather be at our own house than staying at some other people's houses," he said.
His wife, Meagan Harrington, gave him a wry smile. About 10 of their neighbors declined to evacuate, she said.
"They said they wouldn't force you, but it was strongly encouraged," she said.
Shultz teared up behind his sunglasses as he compared his situation to that of his neighbors.
"At least all of our stuff's there and will be there when we get back. The people right by the river, their houses were washed away. Other people thought their houses were going to be OK, and then they started to go. It's just really devastating."
Across the foothills, rescuers made progress against the floodwaters. But they were still unable to go up many narrow canyon roads that were either underwater or washed out.
On Saturday, the surge of water reached the plains east of the mountains, cutting off more communities and diverting some rescue operations.
Four people have been confirmed dead since the harrowing floods began Wednesday. And hundreds of others have not been heard from in the flood zone, which has grown to cover portions of an area nearly the size of Connecticut.
Some of those who are unaccounted for may be stranded or injured. Others might have gotten out but not yet contacted friends and relatives, officials said.
But police expected to find more bodies as the full scope of damage becomes clear.
A woman was missing and presumed dead 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.