Montana snowpack through March near 2011 levels

2014-04-09T17:00:00Z 2014-04-10T11:18:04Z Montana snowpack through March near 2011 levelsBy ZACH BENOIT zbenoit@billingsgazette.com The Billings Gazette

Another snowy month across Montana brought the statewide snowpack through March near the levels seen during the same time in 2011. That year, a combination of runoff, heavy rain and warmer temperatures left much of the state scrambling to respond to significant flooding.

According to the monthly water supply outlook report from the U.S. Department of Agriculture’s Natural Resources Conservation Service in Bozeman, as of April 1, Montana was at 143 percent of normal snowpack and 156 percent of the same time last year.

Statewide snowpack, at 22.2 inches of snow water equivalent (SWE), was the second-highest in 34 years of recording. In 2011, SWE over the same time was 20.9 inches.

However, the NRCS report cautioned that while levels might be slightly above those in 2011 in most areas, it doesn’t mean similar flooding will happen.

In 2011, the time after April 1 is, according to the NRCS, “where the faucet turned on,” with higher-than-usual continued snowpack increases, a handful of heavy rainstorms causing significant runoff and temperatures warming enough in May to start snowmelt and peaking later than normal in June.

“Currently there are no indications of weather that will cause the events seen in 2011,” the report said. “Regardless, snowpack and streamflow runoff needs to be closely monitored for the remainder of this spring until the majority of mountain snow has run into the rivers of Montana.”

Precipitation across the state was the same in March as in February. Only two sub-basins — the Wind River basin in Wyoming leading into the Bighorn River and the West Fork of the Bitterroot River — saw small decreases in snowpack, while the rest of them saw increases.

“March snowpack accumulation continued the trend February set last month by increasing snowpack an average 13 percent across the watersheds of the state,” the report said.

The upper and lower Yellowstone River basins were at 157 and 143 percent of normal snowpack and 174 and 168 percent of 2013, respectively. They combined to put the entire Yellowstone basin at 150 percent of normal and 171 percent of 2013.

In the upper basin, the Red Lodge-Rock Creek basin is the highest it has ever been for SWE, at 203 percent of normal, while the Shields River basin is at 168 percent of normal.

Streamflow forecasts for the lower basin bumped 20 percent over the last month, to 138 percent of normal.

In the Bighorn Range in the lower Yellowstone basin, areas have seen 165 to 181 percent of normal March snowfall and SWE totals across the entire lower basin were the third most in 34 years of record keeping.

The April-July streamflow forecast for the lower Yellowstone basin is 159 percent of average, up 25 percent from March 1.

In the combined Smith, Judith and Musselshell river basins, snowpack finished the month at 160 percent of normal and 167 percent of last year.

The Musselshell drainage saw a noticeable jump from last year, up 592 percent, due largely to the fact that it was at just 27 percent of normal at the same time in 2013.

Streamflow forecasts are also up for the entire basin, at 215 percent of average and 420 percent of last year, assuming average precipitation through July.

Across the Missouri River basin, March set a new SWE record for April 1 thanks to 173 percent of average snowfall, although it hasn’t topped the total record set in 2011. Overall it is at 160 percent of normal, 168 percent of last year and up 14 percent from last month, the report states.

The streamflows could be at 148 percent of average, according to the report’s forecast, and 199 percent of last year.

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