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News Release

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Brian Domonkos

406-587-6991


April 1 Low Elevation Snowpack Drags Down Statewide Average

 

 


Bozeman--Entering the month of March most basins around the state of Montana were near to slightly below normal, with the St. Mary-Milk River Basin having the highest percentage of basin normal at 108 percent, and the Bitterroot River Basin with the lowest percentage at 85 percent, according to snow survey data from the USDA Natural Resources Conservation Service (NRCS).

Through the month, the weather patterns continued to favor the northern basins in the state while the central and southern parts of the state experienced long periods of high pressure, which led to above average temperatures and below average precipitation. Central and southern basins saw a 3 to 9 percent decrease in basin percentage of normal while the basins in northern Montana saw a 4 to 7 percent gain in basin percentage of normal.

As of April 1, the St. Mary-Milk River Basin continues to have the highest percentage of normal at 106 percent, and the Bitterroot River Basin continues to be the lowest at 84 percent. “Overall, the variability in the weather patterns across the state balanced out during the month of March changing the statewide percentage of normal only 1 percent below where it was just a month ago on March 1,” said , NRCS water supply specialist. “That slight change brought the state to 92 percent of normal.”

Snowpack typically reaches its maximum during the month of April so weather in April has a big impact on the timing and volume of stream flows through the spring and into the summer. According to NRCS, warm weather experienced during the end of the month of March has begun to melt low-elevation snowpacks in most parts of the state. “The mid and upper elevations are still holding on, but are slowly beginning to trend in this direction,” Domonkos said. “Continued warm weather will most likely continue to change the snowpack at these elevations to isothermal, starting the larger scale runoff process.”

The mid and upper elevations of the basins yield the bulk of the water supply across the state, so continued monitoring of the snowpack will be required to determine the timing and volume of this year’s runoff.

Snow Water Content
River Basin Percent of Median Percent Last Year March Percent Change
Columbia 93 82 1
 - Kootenai, Montana 100 84 7
 - Flathead, Montana 99 87 5
 - Upper Clark Fork 85 77 -5
 - Bitterroot 84 73 -1
 - Lower Clark Fork 94 82 5
Missouri 92 94 -5
Missouri Headwaters 90 100 -6
 - Jefferson 89 101 -9
 - Madison 89 100 -3
 - Gallatin 94 107 -6
Missouri Mainstem 95 83 -3
 - Headwaters Mainstem 95 77 -5
 - Smith-Judith-Musselshell 95 99 -6
 - Sun-Teton-Marias 88 72 -3
 - Milk (Bearpaw Mountains) 149 184 24
St. Mary 99 94 -2
St. Mary and Milk 106 114 4
Yellowstone 88 73 -2
 - Upper Yellowstone 90 80 -2
 - Lower Yellowstone 85 68 -4
Statewide 92 85 -1

If you encounter any problems with the files provided on this page, please contact Brian Domonkos at .

For detailed snowpack information go to:
Basin-Wide Snowpack Summary (TXT; 64 KB)

Given the current snowpack in place and near normal future precipitation and temperatures, streamflows are predicted to be below average in most basins this season. The table below provides normalized streamflow forecasts for each basin.

Below are the averaged river basin streamflow forecasts for April 1 through July 31. These forecasts assume near normal moisture and runoff conditions April through July.

Streamflow Forecasts
River Basin April to July this Year Percent of Average April to July Last Year Percent of Average
Columbia 88 109
 - Kootenai 96 114
 - Flathead 98 111
 - Upper Clark Fork 77 106
 - Bitterroot 80 104
 - Lower Clark Fork 85 109
Missouri 80 96
 - Jefferson 68 84
 - Madison 87 95
 - Gallatin 89 90
 - Missouri Mainstem 80 89
 - Smith-Judith-Musselshell 75 101
 - Sun-Teton-Marias 92 119
 - Milk 87 87
St. Mary 106 119
Yellowstone 78 91
 - Upper Yellowstone 82 93
 - Lower Yellowstone 75 89
Statewide 83 101

NOTE: The "April-July Last Year Percent of Average" column above is what was forecast last year, NOT what actually occurred.

For detailed basin streamflow forecast information go to:
Provisional Water Supply Forecasts (TXT; 24 KB)

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