A slow-moving low pressure system accompanied by unusually-large amounts of moisture affected Montana on the 16th through 19th of June. This system resulted in widespread steady to heavy rainfall across southwest and north-central Montana. The highest rain totals were concentrated along the Rocky Mountain Front, where up to about 8-inches of storm-total rainfall were recorded and resulted from northeasterly to easterly low-level upslope flow enhancing precipitation. Numerous rivers flooded and Rogers Pass was closed for a time due to excessive runoff and a debris flow. Flooding impacts lingered for several days beyond the 19th, including flooding along the Sun River, as it took time for runoff to travel downstream.

Flood in LEWIS AND CLARK, MONTANA
From 20-JUN-18 08:52:00 to 20-JUN-18 08:52:00 (MST-7)
Location: LINCOLN ARPT
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported flood water was still flowing across Rogers Pass and the pass remained closed. Excessive runoff from significant rainfall on June 16th through 19th and debris from a recent wildfire burn scar clogged culverts along the pass, leading to erosion and unstable road conditions.

Flood in LEWIS AND CLARK, MONTANA
From 19-JUN-18 07:21:00 to 19-JUN-18 07:21:00 (MST-7)
Location: AUGUSTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Report of 8 to 12-inches of floodwater along Main Street in Augusta due to Elk Creek overflowing its banks.

Flood in LEWIS AND CLARK, MONTANA
From 19-JUN-18 12:18:00 to 19-JUN-18 12:18:00 (MST-7)
Location: FT HARRISON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Multiple media outlets reported flooding along Tenmile Creek near McHugh Lane in Helena. Roadways were flooded and water was waist-deep in some areas.

Flood in LEWIS AND CLARK, MONTANA
From 19-JUN-18 12:19:00 to 19-JUN-18 12:19:00 (MST-7)
Location: CRAIG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported flooding at multiple fishing access sites along Dearborn River and downstream portion of Missouri River near Craig.

Flood in CASCADE, MONTANA
From 19-JUN-18 11:00:00 to 19-JUN-18 11:00:00 (MST-7)
Location: MID CANON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported flooding along Dearborn and Missouri Rivers. Water levels were highest he had ever seen. Flooding caused minor fence damage on his property.

Flood in LEWIS AND CLARK, MONTANA
From 20-JUN-18 08:51:00 to 20-JUN-18 08:51:00 (MST-7)
Location: LINCOLN ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported Blackfoot River overflowing its banks 8-miles ENE of Lincoln. Highest river level seen all year and water was nearing houses.

Flood in BROADWATER, MONTANA
From 20-JUN-18 11:40:00 to 20-JUN-18 11:40:00 (MST-7)
Location: RADERSBURG
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Broadwater County Emergency Manager reported flooding along Highway 285. Floodwater was from Crow Creek overflowing its banks.

Flood in CASCADE, MONTANA
From 21-JUN-18 10:35:00 to 21-JUN-18 10:35:00 (MST-7)
Location: SUN RIVER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Great Falls hydrologist reported and photographed flooding in the town of Sun River due to the Sun River flowing out of its banks.