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Brian Domonkos

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June 1 Persistent Snowpack Begins to Melt While Remaining Well Above Average

June 1 Persistent Snowpack Begins to Melt While Remaining Well Above Average


 


Bozeman--With continued La Nina-like weather patterns through the month of May 2011, the snowpack of Montana maintained well above average conditions, according to the USDA Natural Resources Conservation Service (NRCS).

Below average temperatures have resulted in low snowmelt rates, ultimately allowing seasonal snowpack to remain on the ground, in some locations later than ever before. Typically, more than 50 percent of the automated SNOTEL sites are void of snow at this point in the year.

“Presently, almost three quarters of the automated snow measuring sites in Montana and northern Wyoming still hold considerable snowpack,” said Brian Domonkos, NRCS water supply specialist. “In fact, some individual SNOTEL sites, especially the high elevation sites of northern Wyoming, reached this year’s maximum snowpack in the last two days of May.”

SNOTEL data indicates a significant amount of snow remains in the mountains primed for runoff into streams and rivers, and most basins have yet to reach streamflow peak due to snowmelt.

Snow Water Content
River Basin Percent of Average Percent of Last Year April percent Change
Columbia 237 235 +77
Kootenai, Montana 249 289 +80
Flathead, Montana 235 196 +55
Upper Clark Fork 240 205 +86
Bitterroot 207 381 +57
Lower Clark Fork 288 413 +121
Missouri 261 192 +108
Missouri Headwaters 240 188 +97
 - Jefferson 228 170 +97
 - Madison 218 193 +73
 - Gallatin 244 187 +101
Missouri Mainstem 328 195 +148
 - Headwaters Mainstem 300 207 +143
 - Smith-Judith-Musselshell 386 152 +198
 - Sun-Teton-Marias 273 326 +107
 - Bearpaw Mountains -- -- --
St. Mary 170 161 +28
St. Mary and Milk 167 161 +28
Yellowstone 268 219 +123
Upper Yellowstone 222 217 +71
Lower Yellowstone 305 227 +166
Statewide 243 219 +83

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

See the following text document for detailed basin snowpack information:

Basin-Wide Snowpack Summary (TXT; 64 KB)

June 1 streamflow forecasts are a reflection of the current above average snowpack conditions. Assuming average future precipitation and temperatures for the remainder of the snowmelt season, streamflows volumes are forecast to be well above average across all basins within Montana.

Below are averaged streamflow forecasts, by river basin, for the period June 1 through July 31. These forecasts assume near normal spring conditions and do not account for well below average (70 percent or less) or well above average (130 percent or more) snowmelt or spring rain.

Streamflow Forecasts
River Basin May to July this Year Percent of Average May to July Last Year Percent of Average
Columbia 188 78
-- Kootenai 168 68
-- Flathead 200 93
-- Upper Clark Fork 194 77
-- Bitterroot 162 71
-- Lower Clark Fork 183 66
Missouri 191 88
-- Jefferson 183 78
-- Madison 149 64
-- Gallatin 156 87
-- Missouri Mainstem 173 79
-- Smith-Judith-Musselshell 251 124
-- Sun-Teton-Marias 194 73
-- Milk 193 117
St. Mary 155 93
Yellowstone 200 88
-- Upper Yellowstone 170 79
-- Lower Yellowstone 231 101
Statewide 190 84

NOTE: The "June to July Last Year Percent of Average" column above is what was forecast last year on June 1 and NOT what actually occurred.

See the following text document for detailed basin streamflow forecast information:

Provisional Water Supply Forecasts (TXT; 24 KB)

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