High-Impact Weather and Climate Events

21 Mile Dam. Cause of failure: Rain-on-snow flooding. The 21 Mile Dam failure occurred in northeastern Nevada but impacted northwestern Utah from subsequent flooding and the rain-on-snow event.

"The 21 Mile Dam failed in Elko County, Nevada on February 8, 2017 due to heavy runoff and snowmelt. The water broke free from the earthen dam and flooded the community of Montello, Nevada, damaged Union Pacific property, and entered extreme northwestern Utah causing road damage." - Utah DEM

"On February 6, 2017, a combination of a strong Pacific trough and cold front, an ample supply of moisture combined to bring very heavy snow to much of western Wyoming. The highest amounts fell in the Tetons where almost 3 feet of new snow occurred at the Jackson Hole Ski resort. Heavy snow also fell in the Salt and Wyoming Range where 32 inches of snow occurred at the Indian Creek SNOTEL. Other heavy snowfall amounts included 25 inches at Deer Creek in the Wind River Range, 18 inches at Two Oceans Plateau in Yellowstone, 16 inches near Wilson, and 8 inches in Cody Alpine. The heavy snow combined with gusty winds to produce very low visibility and avalanches that shut down many roads including Teton Pass, Hoback Junction and South Pass. In Jackson, the heavy snow load caused the collapse of the roof onto the Sears Department Store. In addition, strong winds occurred on the evening of the 7th. These strong winds combined with heavy wet snow to down 17 power poles along Highway 390. This led to a power outage that lasted through the 11th. Near Teton Village, strong winds estimated over 70 mph, combined with heavy snow to down 17 power poles which led to a power outage lasting through the 11th. Jackson Hole Ski resort was closed through Monday the 13th. Meanwhile, strong wind occurred east of the Divide and across southern Wyoming. The maximum wind gusts included 96 mph at Camp Creek in the Green and Rattlesnake Range, 72 mph near Lander and 65 mph along Outer Drive south of Casper." - WY Hazard Mitigation Plan 2021-2026

"Freezing rain was first detected in the Steamboat Springs area around 2 in the morning, where over 4600 customers went without power due to a downed feeder line west of Clark likely caused by a coating of ice on the power lines due to freezing rain. Then between 4 am and 6 am, freezing rain occurred in La Plata County in southwest Colorado as well as the Grand Valley through Glenwood Canyon in west-central Colorado. This resulted in icy roads, numerous slide offs and accidents and major highways to be closed for the majority of the day due to accidents and cleanup activities, including Interstate 70 from Grand Junction to Glenwood Springs and Highway 160 from Durango to Hesperus Hill. Impacts were felt not only with the morning commute, but also at dispatch centers and hospitals that were overwhelmed. Emergency rooms at various hospitals throughout the Grand Valley, including Grand Junction, exceeded their daily admittance records with over 200 people treated for broken bones and other blunt force injuries due to the icy surfaces. Schools were also closed throughout the Grand Valley and many businesses were negatively impacted by either not opening, opening late or the lack of customers. This was the first day back from winter break for Mesa County schools, which in addition to the icy road impacts, crippled transportation. The Grand Junction Regional Airport also closed for several hours due to the ice, resulting in a few diverted flights." - National Weather Service

"On October 16, 2016, strong, moist westerly flow off the Pacific Ocean brought abundant moisture to the mountains and valleys of western Wyoming. The precipitation fell as snow in the mountains, with the heaviest snow of 12 to 18 inches falling in the Salt River, Wyoming, and western Wind River ranges. The position and strength of a jet streak helped to produce and sustain persistent snow in a swath from Big Piney to Pinedale in Sublette County. Snowfall rates reached up to 2 inches an hour during the late evening of Sunday, October 16, and early morning hours of Monday, October 17. Totals within this heavy snow band ranged from 8 inches to 15 inches with the greatest totals from around Daniel to Pinedale. In Big Piney, the heavy, wet snow caused the collapse of a school bus building roof resulting in $15,000 in damages. East of the Continental Divide the story was strong downslope wind. Wind gusts in the Lander Foothills topped 70 mph with a peak of 80 mph along the North Fork of the Popo Agie River. The strong winds blew over a tree in a Lander residential area." - WY Hazard Mitigation Plan 2021-2026

Sixth most damaging hail storm in Colorado history. "This storm was concentrated in the Colorado Springs area and the size of the hail resulted in a very high percentage of claims that were total losses." - The Gazette

"A powerful blizzard developed across the Front Range of Colorado late Tuesday, March 22, and continued through much of Wednesday, March 23, 2016. The storm tracked east/southeast across Utah Tuesday afternoon and evening, and then into Southeast Colorado by Wednesday morning. The storm rapidly intensified as the storm reached eastern Colorado, producing extremely heavy and intense snowfall with snowfall rates exceeding 3 inches per hour at times. In addition to heavy snow, strong winds gusting in excess of 50 mph east of Interstate 25 produced widespread blizzard conditions and zero visibilities. Further south across southern Colorado, peak wind gusts were between 70-80 mph." - National Weather Service

Moisture from the remnants of Hurricane Linda spread into the Southwest and intersected with a strong upper-level trough, sparking isolated heavy thunderstorms. Two successive storms passed over Hildale between 2:00 pm and 5:00 pm, dropping an estimated 2" in rain. This caused two flood peaks on Short Creek in Hildale, the second of which swept away two vehicles with 16 people inside, 13 of whom drowned. The second storm also produced heavy rain in Zion National Park, about 15 miles north of Hildale, causing a flash flood in Keyhole Canyon that killed seven park visitors who were canyoneering. Another motorist 15 miles west of Hildale was swept away and killed by flooding the same day.

"Morgan and Washington Counties Levee Breach, 2015: On June 15, 2015, a levee breach, about 100 yards wide along the South Platte River, produced farmland flooding over northeast Morgan and northwest Washington Counties. Floodwaters, three to four feet deep, washed out the Union Pacific railroad tracks southwest of Messex. Up to ten inches of water covered several miles of track. Approximately 30 trains per day had to be diverted until the tracks could be repaired and inspected. Washington County Road 58.3 was also washed out." - CO Hazard Mitigation Plan 2018-2023

"Severe thunderstorms broke out across Boulder, Denver, Elbert, Jefferson and Larimer Counties. Two large and long lived tornadoes developed in Larimer County near Berthoud and near Simla in Elbert County. The tornado that occurred along the Boulder and Larimer county line was rated an EF3 at its highest damage point, with maximum winds estimated at 135 to 140 mph. The path length was 6 miles long with a width of one quarter mile at times. In Elbert County, 17 tornadoes touched down, with EF1 damage observed southwest and southeast of Simla. Four homes suffered severe damage; two were uninhabitable. In addition, two other homes suffered moderate damage with slight damage reported to eight other residences. Large hail up to baseball size occurred in Elbert County, with hail up to tennis ball size observed in Boulder County. The hail damaged cars and homes; breaking windows and windshields. The tornado continued its track into Larimer County. At least 25 homes between Longmont and Berthoud were damaged; three of them destroyed. No injuries were reported as the winds tore apart homes and rolled vehicles." - NOAA

Part of NCDC's billion-dollar disaster list. Estimated to be the eighth-most costly hailstorm in Colorado history.