On the weekend of June 11th and 12th, a stationary front set up across northwestern Wyoming. On June 12th into June 13th an atmospheric river fed moisture into a powerful jet steam along the front and brought an extended period of moderate rain along with occasional heavy rain due to embedded thunderstorms.
Preceding this event, April and May were cool and wet, with above normal precipitation and below normal temperatures. This time period included a large storm that brought 2 to 3 feet of snow for many locations above 8000 feet in the mountains of Yellowstone National Park and the Absaroka Mountains. This late season snow event added a large amount of water content to the snowpack.
In the days preceding the flood, many areas experienced well above normal temperatures that brought rapid snowmelt and rises in river levels. In the highest elevations, the snowpack did not decrease notably from the warm temperatures, but was ripened, and primed for later melting due to rain. The rain on the 12th and 13th accelerated the melt and quickly brought rivers over their banks. The result was record flooding, especially across the northern half of Yellowstone. Over 10,000 visitors had to be evacuated from the Park. Numerous roads and trails, mainly in the northern portion of the Park, were damaged or completely washed out. The northern entrance to the Park, which follows the Gardner River through a steep canyon, was completely destroyed in several locations where the fast flowing river's momentum cut into the adjacent steep terrain on which the road was built. The northeastern entrance was also closed due to mud and rockslides as well as flood damage. North of Yellowstone, in southern Montana, rainfall was equally extreme, with communities such as Red Lodge, MT and Gardiner, MT being affected. Flooding and damage also occurred in the southern half of Yellowstone National Park, although damage was much less severe since rainfall was less intense further south.
The extensive flooding and damage led to the entire park being closed for 10 days at the height of tourist season. The southern loop reopened to limited numbers of tourists on June 22nd, and over 90 percent of Park roads reopened by July 2nd. The north and northeast entrances remain closed to most traffic as of early August 2022. A Yellowstone Park press release described the flood as a 500-year flood event. No deaths or injuries were reported from the flooding in Yellowstone. Damages were extensive, but no monetary estimates were available at the time of publishing this report.