A slow-moving upper level low south of Wyoming sent waves of moisture northward over central and eastern Wyoming during the Memorial Day holiday weekend. Measured and estimated rainfall totals ranged from two to around five inches. This resulted in flooding and flash flooding in several areas. Johnson County saw significant flooding along the tributaries and main stem of the Powder River and around Buffalo. The greatest impact was felt in Hot Springs County where heavy rains in the Wind River Canyon resulted in several mud and rock slides that closed State Highway 789 between Thermopolis and Shoshoni. The slides also damaged several sections of railroad track in the same area subsequently shutting down rail traffic. Minor flooding was also noted in Fremont County where water approached homes in low lying areas of Lyons Valley near Lander.

Flash Flood in HOT SPRINGS, WYOMING
From 24-MAY-15 18:30:00 to 24-MAY-15 20:00:00 (MST-7)
Location: THERMOPOLIS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain caused flooding near the town of Thermopolis. South of Thermopolis, Buffalo Creek overflowed its banks and flooded nearby low lying areas. A mobile home community experienced flooding in East Thermopolis as small creeks and streams were inundated with water.

Flash Flood in HOT SPRINGS, WYOMING
From 24-MAY-15 14:10:00 to 25-MAY-15 08:30:00 (MST-7)
Location: THERMOPOLIS
Flood cause: Heavy Rain
Property damage: 1.50M
Crop damage: 0.00K
Reported by: Department of Highways

Very heavy rain fell in southern Hot Springs County. This triggered numerous mud and rock slides, some tumbling several hundred feet or more to the bottom of the Wind River Canyon. State Highway 789 through the canyon was covered with mud, rock, and debris in several locations between mileposts 120 and 123. One Wyoming Department of Transportation employee was briefly trapped in his front-end loader as he tried to clear away small slides at the onset of the event. The massive amount of debris on the highway resulted in the closure of the road from Sunday afternoon, May 24, until Wednesday morning, May 27. Additional slides on the west side of the Wind River Canyon destroyed several sections of railroad track that resulted in a halt of train traffic for several days.

Flood in JOHNSON, WYOMING
From 24-MAY-15 19:30:00 to 25-MAY-15 21:20:00 (MST-7)
Location: KAYCEE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 250.00K
Reported by: River/Stream Gage

Heavy rain fell in the tributaries of the Powder River in southern Johnson and northern Natrona counties. The South Fork of the Powder River along with Salt Creek were two of the major contributors to a rapid rise in the water level of the Powder River near Sussex. High water on both the North and Middle forks of the Powder River also served to flood the main stem. The river climbed more than 10 feet in less than 24 hours at Sussex and crested at 15.63 feet around 0500MST on Monday, May 25. This crest topped the previous record crest of 15.16 feet set in May 1978. Agricultural land downstream of Kaycee near Sussex was completely inundated and several ranches and vehicles were surrounded by water.

Flash Flood in JOHNSON, WYOMING
From 24-MAY-15 15:00:00 to 24-MAY-15 19:00:00 (MST-7)
Location: KAYCEE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Heavy rain fell across southern Johnson County and brought flooding to the tributaries of the North Fork and Middle Fork of the Powder River. Flooding was observed between Mayoworth and Kaycee and also between Barnum and Kaycee.

Flash Flood in FREMONT, WYOMING
From 24-MAY-15 15:30:00 to 24-MAY-15 18:00:00 (MST-7)
Location: LANDER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rainfall led to flooding in Lyons Valley near Lander. The Little Popo Agie River overflowed its banks and flooded low lying areas along Lyons Valley Road. The water approached some homes along the river but did not enter them.

Flood in JOHNSON, WYOMING
From 25-MAY-15 06:00:00 to 26-MAY-15 23:00:00 (MST-7)
Location: SUSSEX
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A flood wave moved north down the Powder River as a result of heavy rain over the Memorial Day Weekend. For the most part, impacts were confined to low lying land nearest the river. However, there was flooding of some infrastructure near the Interstate 90 Powder River bridge in eastern Johnson County.

Flash Flood in NATRONA, WYOMING
From 24-MAY-15 13:00:00 to 24-MAY-15 18:00:00 (MST-7)
Location: SALT CREEK COLUMBINE
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Social Media

Several storm spotters reported flash flooding on Salt Creek and Castle Creek in the vicinity of Midwest. Some county and Bureau of Land Management roads were washed out. At least one fracking trailer was destroyed south of town.

Flash Flood in NATRONA, WYOMING
From 24-MAY-15 15:30:00 to 24-MAY-15 16:30:00 (MST-7)
Location: BAR NUNN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotters reported flood waters up to buildings on the south side of Bar Nunn.

Flood in JOHNSON, WYOMING
From 24-MAY-15 19:00:00 to 25-MAY-15 08:00:00 (MST-7)
Location: BUFFALO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rainfall of two to three inches fell across northern Johnson County and caused flooding along Clear Creek. The flooding was mainly over low lying fields and caused little to no damage.