Heavy snowpack, rain, warming trend will conspire to raise river levels
Spring Runoff 4
On Tuesday, May 10, the East Gallatin River jumped its banks along Dry Creek Road north of Belgrade and began causing minor flooding in lowland pastures. With area mountain ranges loaded with snow and warmer temperatures on the way, weather watchers say parts of southwestern Montana could see major
It may not be biblical, but with mountain snowpack at upwards of 200 percent of normal, this year’s spring runoff is expected to be epic, or at the very least, recordbreaking, the National Weather Service said Monday.
The mercury is expected to rise into the mid-60s later this week, and coupled with recent rains and heavy mountain snowpack, a “perfect storm” could be brewing. The waters of the West Gallatin River are expected to rise to flood stage and beyond by Saturday, and weather watchers expect moderate flooding at Gallatin Gateway and other areas.
A National Weather Service spokeswoman said Monday the flooding we will see this season could set new records, and emergency managers have wasted no time in urging residents to get ready.
Mountain snowpack in the Gallatin, Madison and Jefferson river basins are “above to well-above normal,” and in some areas the snow-water content is higher than we have seen in more than 40 years, said Gina Loss, a senior service hydrologist for the Great Falls Weather Forecast Office.
Loss spoke during a Monday afternoon Webcast, and called on the media to alert the public about the threat.
“Pretty much the entire state has more water than they know what to do with,” she said.
In a warning issued Monday, Gallatin County emergency manager Patrick Lonergan said property owners should be preparing for imminent high water.
“The current and predicted weather, combined with the snow pack, has set up Gallatin County to be susceptible to flooding in the immediate future,” he said.
Owners of property that has flooded in the past “should be preparing now to protect their property. Once flooding occurs it is usually too late to do much good ...”
Most of the mountains whose snowpack feed river basins throughout southwestern are holding record or near-record snow-water, which determines how full rivers and streams will get during runoff, Loss said.
“Most basins are holding 18 to 30 inches of water in that snow,” she said. “And we’re pushing later and later as far as when this water should be coming out.”
But lower-than-normal temperatures have kept snow in the mountains, and wetter-than-normal conditions have packed more snow in.
In the Jefferson River basin, the current snow-water level hasn’t been seen since 1975, Loss said. “Again, none of it’s really coming out yet.”
The story is the same in the Madison and Gallatin river basins, where snowpack is hovering from 140 to 160 percent of normal, and snow-water content is at more than 56 percent in some places, she said.
The National Weather Service is predicting a “better than 98 percent chance” of moderate to major flooding on the Gallatin, Madison and Jefferson rivers, Loss said.
“The worst flooding we expect starting next week and continuing for about the next four or five weeks,” she said. “It’s going to be a long haul.”
With recent rains, the Gallatin is expected to come up as temperatures begin to rise, and will reach its six-foot flood stage Friday or Saturday. The story is the same for the Jefferson River at Three Forks, where flood stage is eight feet.
“We are seeing some stream rises just with the precipitation we are having and with the warmer temperatures we’ve had before this storm moved in, so things are starting to change. Our chances for any type of flooding are just really good.”
Sandbags are available for purchase from several local hardware stores, Lonergan said. Stores that have indicated sandbags are in stock include Bozeman Brick and Tile, Belgrade True Value, Lowe’s and Big Sky True Value. More information on flood preparation is at readygallatin.com.
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