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News Release

June Montana Snowpack Ends Season Below Average, Low Steamflows Likely to Follow

June 6, 2013
Brian Domonkos

Bozeman--The transition into spring is in full swing across the state of Montana causing water levels to rise in rivers and streams and flowers to bloom in the valleys. During the first two weeks of the month significantly above average temperatures transitioned Montana’s snowpack to an active snowmelt regime at all but the highest elevations, according to snow survey data from the USDA Natural Resources Conservation Service (NRCS).

The high daily average temperatures and overnight above freezing temperatures were substantial enough to cause above average snowmelt rates across the state, causing rivers and streams to rise, and in most cases, reach their snowmelt driven peaks during the middle to latter part of the month. “There may be a few river systems that have yet to see their peak, systems where peaks are typically driven by the high elevation component of snowmelt,” said Brian Domonkos, NRCS water supply specialist.

Based on SNOTEL (SNOw TELemetry) data on June 1, current basin average Snow Water Equivalents across the state range from 44 to 64 percent of this year’s maximum. Domonkos said the remaining snowpack will help to sustain flows through spring snowmelt and into the summer.

The abundance of precipitation during the second half of May was a change to the first two weeks of warm and dry weather, and helped some watersheds east of the Divide improve their water year-to-date precipitation. Most basins across the state continue to be near normal for water year-to-date precipitation with the Milk basin having the highest basin average at 132 percent.

The basins in the furthest reaches of southwest Montana continue to have the lowest basin water year-to-date averages with the Jefferson and Madison River basins both at 88 percent. Low snowpack totals in the Jefferson River basin contributed to this low precipitation average, even though the month of May was 97 percent of average for mountain precipitation.

Montana saw a large range in May precipitation--from 48 percent of May average in the Bitterroot River basin to 112 percent in the Missouri Mainstem River basin south of Helena. The weather patterns experienced during the last two weeks of May favored the valleys of central, northeastern and the southern Montana, dropping substantial storm totals during the events.

“The timing of precipitation is critical to the greater water system as this is the time of the year when dam tenders are filling reservoirs, while irrigators begin to draw water,” Domonkos said. “Continued precipitation during the month of June will certainly be welcome starting into the hot summer months and persistent active storm patterns become less frequent.”

Snow Water Content
River Basin Percent of Median Percent Last Year May Percent Change
Columbia 89 56 -17
Kootenai, Montana 93 44 -22
Flathead, Montana 102 66 -13
Upper Clark Fork 72 53 -21
Bitterroot 38 34 -57
Lower Clark Fork 108 53 -6
Missouri 67 63 -31
Missouri Headwaters 67 72 -28
 - Jefferson 67 86 -22
 - Madison 63 69 -31
 - Gallatin 80 80 -25
Missouri Mainstem 65 44 -39
 - Headwaters Mainstem 34 36 -63
 - Smith-Judith-Musselshell 61 45 -42
 - Sun-Teton-Marias 86 47 -24
 - Milk (Bearpaw Mountains) -- -- --
St. Mary 114 80 -4
St. Mary and Milk 114 75 -4
Yellowstone 68 65 -37
Upper Yellowstone 64 58 -36
Lower Yellowstone 63 71 -44
Statewide 76 60 -29

If you encounter any problems with the files provided on this page, please contact Brian Domonkos at 406-587-6991.

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

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

Streamflow Forecasts
River Basin June to July Forecast Percent of Average June to July Forecast Percent of Last Year Observed
Columbia 89 64
Kootenai 96 53
Flathead 96 63
Upper Clark Fork 68 66
Bitterroot 68 67
Lower Clark Fork 84 64
Missouri 74 64
Jefferson 48 100
Madison 74 86
Gallatin 96 126
Missouri Mainstem 75 106
Smith-Judith-Musselshell 70 222
Sun-Teton-Marias 94 92
Milk 87 54
St. Mary 108 80
Yellowstone 80 64
Upper Yellowstone 85 93
Lower Yellowstone 75 112
Statewide 83 78

NOTE: The June-July Forecast Percent of Average column above reflects this year’s forecasts as a percent of last year’s observed streamflow, using only those locations which have data available for last year.

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


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