PROJECT ALERT NOTICE (MT) Flooding continues in eastern Montana

Date: Tue, 26 Mar 2019 15:29:16 EDT

Summary: Minor to major flooding from snowmelt-runoff and ice-jams continues in eastern Montana.

Gage-heights at eleven (11) U.S. Geological Survey streamgages in eastern Montana are exceeding National Weather Service (NWS) minor to major flood stages. Lowland snowmelt-runoff and ice-jams are the cause of most of the flooding, exacerbated by frozen soils resulting from cold temperatures (see https://www.ncdc.noaa.gov/monitoring-content/sotc/national/grid-temp/tave-anom-201902.png). Previously reported flooding in the Milk River basin and tributaries will continue to intensify through the week according to NWS forecasts, with one tributary streamgage currently exceeding major flood stage [no change]. NWS is forecasting the flood crest on the Missouri River above Fort Peck Reservoir to be one of the top five for the period of record. Flooding from ice-jams on the Yellowstone River in Montana is no longer occurring. Flooding continues along the Little Bighorn River and Little Missouri Rivers in southeastern Montana where many roads are closed including Interstate 90.

Four crews of two hydrographers will be completing high-flow measurements today. Gage heights at 14 streamgages in Wyoming and Montana are greater than the 99th percentile for the date. Annual exceedance probabilities have not been determined as streamflows are expected to increase at some streamgages.

Cooperators, stakeholders, and the general public are being kept informed by multiple methods including NWSChat, telephone conversations, e-mail, and social media. Photographs of hydrographers measuring flood- and high-flows with text for context and links to data are being posted at Twitter and Instagram accounts @USGS_WY and @USGS_MT. Analytics indicate posts to Twitter in particular are receiving relatively high levels of attention.

Interactive flood map for the Milk River, northeastern Montana