Flood — Blaine, Montana

2023-04-10 to 2023-04-14 · near Chinook, Blaine, Montana

Event narrative

Significant flooding occurred along the Milk River across Blaine County. The Rocky Boy SNOTEL station which is the main Milk River basin station peaked later than normal and had over 3.5 times the snow water equivalent that it normally would on April 6 (10.7' of snow water equivalent versus a normal of 3.0'). When this thick snowpack melted, virtually the entire Milk River system flooded in a matter of days, as a result. The Milk River near Harlem crested at 23.80 feet on April 12, which as of this entry was the seventh highest river level recorded at this site. Roughly 4,000 aces of irrigation land was flooded. Chinook water plant was surrounded by water. Several roads and homes were impacted.

Wider weather episode

Unseasonably warm temperatures occurred in the first two weeks of April, with highs near 80 degrees occurring at times. These warm temps, along with occasional rain, resulted in melting of a deep snowpack on top of frozen ground which led to significant runoff into area waterways. Moderate to major flooding occurred along portions of the Milk River and its tributaries. Impactful snowmelt flooding also occurred across Southcentral Montana, in particular across the Gallatin Valley.

View location on OpenStreetMap → (48.6102, -109.2130)

Source: NOAA Storm Events Database, event_id 1096940. Narrative written by the NWS forecast office that issued the report.