Late winter storms are packing a punch to the Rockies, piling snowpack on top of already record levels across the West where officials are concerned about historic flooding, avalanches and mudslides.
"At this point, everybody is just sitting back chewing fingernails and waiting because the longer it stays cold and wet, the worse it's going to get," said Randy Julander, a supervisor with the U.S. Department of Agriculture's Natural Resources Conservation Service.
Julander said in a typical year the weather warms gradually, allowing snow in the mountains to melt slowly and ease into rivers and streams over time. That's not the case this year.
"June is right around the corner and sooner or later, it's going to warm up," he said, noting that instead of gradually warming over eight to ten weeks, the West will likely see a rapid rise in temperatures heading into summer, a worst case scenario.
"And it's not just Utah, Colorado and Wyoming. It's basically all of the western states except Arizona and New Mexico," Julander said. "We're waiting for the chute to open and the bull to come out bucking, but he ain't moving, yet."
The northern Utah mountains could see up to a foot of fresh snow this week with a weather system that is dropping rain elsewhere and will soon head toward Colorado and Wyoming.
A slew of flood warnings have already been issued. The National Weather Service says up to 3 inches of rain is predicted in parts of southeast Wyoming, while up to a foot of snow is forecast for the mountains.
The winter storms are expected to dump up to 18 inches of snow in the northern Colorado mountains, where snowpack is already at up to 200 percent above average.
The record snowpack levels are almost too deep to measure in some parts of northern Colorado and have officials concerned about major flooding across the state's northern corners and down the eastern plains.
A storm Wednesday brought so much hail to an area northwest of Denver that plows were used to clear the roads of marble-sized ice chunks up to 3 inches deep. The thunderstorm also spawned a tornado warning, which expired without any reports of touchdowns.
Authorities said a cold front brought in cooler air combined with moisture, helping create funnel action in the atmosphere.
Mudslides and floods are possible near Boulder, about 30 miles northwest of Denver, and other areas burned by September wildfires that left the landscape charred and at risk of erosion.
Utah has already seen some minor mudslides that have damaged a few homes, and a slide in northwest Wyoming about 25 miles south of Jackson has closed a portion of highway U.S. 26 in the Snake River Canyon. Authorities say it began over the weekend and has covered about 100 yards of the road and spilled into the Snake River.
Utah, Wyoming and Colorado have already seen some minor flooding with recent warm-ups, but many rivers and streams have receded because of the return of cold weather and more snow locking the water back up in the mountains for now.
Snow in the higher elevations, where the greatest snowpack has accumulated, hasn't even begun to melt in most of places.
"But stay tuned, of course, because we're going to make more snow up there," said Jim Fahey, a National Weather Service hydrologist in Wyoming. "It's going to come down sometime and when it does it's going to be a pretty good runoff. We know that."
And Fahey said the latest storm this week will be bringing a lot more.
"More snow up in the mountains if you can believe that, like we need it," he said.
Wyoming's mountain snowpack already is at up to 250 percent of normal in some areas above the state's major river basins, which is where it will all come down eventually in the form of water, likely deluges.
Julander said temperatures across the region have been hovering at 10 to 20 degrees below normal for this time of year and said some parts of the northern Utah mountains have snowpack at 400 percent above normal.
He said the last time the West saw such unusual prolonged cold weather with steady rain and snow was in 1983 when massive flooding across the region caused substantial damage.
"That's when we had terrible flooding in Utah and across the West. The Colorado River went absolutely wild for about a month," Julander said. "The amount of water up there in the mountains is phenomenal and it's going to melt sooner or later. You're looking at an event that certainly only happens maybe once every 20, 30, even 50 years."
Bob Moen in Cheyenne, Wyo. and Sheila V Kumar in Denver, Colo., contributed to this report.