Snowpack Still on the Rise, Well Above Average, and Setting Records in Some Parts of Montana

From NRCS:

Unlike February, snowfall wasn’t record-breaking in Montana during March, but it was sufficient to keep the snowpack near to well above normal on April 1, according to snow survey data collected by the USDA Natural Resources Conservation Service (NRCS). “One thing is for sure; it’s been a snowy winter across the state of Montana,” said Lucas Zukiewicz, NRCS water supply specialist for Montana, “and there’s still more to come.”

Last month, records were set for both monthly totals for February snowfall, and for total snowpack accumulation on March 1. Many snowpack measuring locations that feed Montana’s rivers and streams remain record high for April 1. Ten SNOwpack TELemetry (SNOTEL) and snowcourse locations remain the highest on record for this date, and 12 measurement locations are the second highest on record. These sites can be found in the mountains that feed the Upper Yellowstone River, Upper Clark Fork and Missouri Mainstem River basins, where snowfall has been abundant throughout the winter months. “Although not record-setting like these regions, the snowpack in other river basins across the state is well above normal for this time of year,” Zukiewicz said.

2018 is looking to go down as one of the biggest snow years on record for some parts of the state, prompting questions on how it compares to other memorable snowpack years. “1972, 1997, 2011 and 2014 were all big winters across the state, and many are wondering how this year compares,” Zukiewicz said. “So far, the only snowpack that has topped all other water years for peak snow water contained in the snowpack is the area near Cooke City which feeds the Clark’s Fork River of the Yellowstone River.”

For the most part, the snowpack in the rest of the state hasn’t reached the levels of 1997, 2011 and 2014. “During those years, snowpack peaked at the beginning of May to early June. For now, it looks like there is still a lot of winter left to come and this year could break more records if it keeps going.” Zukiewicz said.

Long-range predictions by the National Weather Service’s Climate Prediction Center continue to forecast above average precipitation and below average temperatures through the end of April.

Due to the abundant snowfall, many measurement locations have already reached, or exceeded, the normal amount of snow water that is typically contained in the snowpack before runoff occurs, all but assuring at least normal surface water supply this spring and summer, Zukiewicz said. Long-duration volumetric streamflow forecasts issued for the April 1 – July 31 period are well above average for most stream gages in the state, and could approach record levels this spring and summer at the stream gage at Belfry, Mont., located along Clark’s Fork of the Yellowstone.

“Having a big snowpack is a double-edged sword,” Zukiewicz said. “You know there will be plenty of snowpack to feed the rivers, which is typically great news, but the uncertainty of how and when it will come out can keep you up at night.”

The coming month will be critical in determining how much water is available in the snowpack for runoff this spring, and the day-to-day and week-by-week weather patterns during May and June will determine the timing and volumes of water in Montana. Water users are encouraged to read the May 1, 2018, NRCS Water Supply Outlook Report, which will summarize the conditions that occurred over the month of April, and help water users prepare for runoff this spring and summer.

Individual point forecasts for streams and rivers can be found in the monthly NRCS Water Supply Outlook Report and should be consulted as conditions vary from basin to basin, and even within the basins themselves.

Monthly Water Supply Outlook Reports can be found at the website below after the 5th business day of the month:

April 1, 2018, Snow Water Equivalent

River Basin % of Normal % Last Year
Columbia 137 134
Kootenai, Montana 128 122
Flathead, Montana 136 130
Upper Clark Fork 156 170
Bitterroot 134 128
Lower Clark Fork 124 117
Missouri 133 145
Jefferson 135 134
Madison 124 118
Gallatin 130 148
Headwaters Mainstem 169 190
Smith-Judith-Musselshell 130 186
Sun-Teton-Marias 142 122
St. Mary-Milk 140 149
Yellowstone River Basin 135 102
Upper Yellowstone 152 128
Lower Yellowstone 121 85
West of the Divide 137 134
East of the Divide 133 119
Montana State-Wide 137 137

April 1, 2018, Precipitation

River Basin Monthly % of Average Water Year % of Average Water Year % of Last Year
Columbia 93 123 95
Kootenai, Montana 93 113 81
Flathead, Montana 101 129 96
Upper Clark Fork 103 130 114
Bitterroot 99 119 100
Lower Clark Fork 69 115 85
Missouri 111 119 95
Jefferson 117 111 93
Madison 121 113 82
Gallatin 113 124 98
Headwaters Mainstem 111 137 120
Smith-Judith-Musselshell 90 117 111
Sun-Teton-Marias 90 136 104
St. Mary-Milk 107 130 88
Yellowstone River Basin 98 122 83
Upper Yellowstone 99 138 95
Lower Yellowstone 98 108 72
West of the Divide 93 123 95
East of the Divide 103 121 89
Montana State-Wide 102 124 95

April-July 50% Exceedance Forecasts

River Basin Highest Point Forecast* Lowest Point Forecast** Basin Average Forecast***
Columbia 231% 107% 134%
Kootenai, Montana 124% 110% 118%
Flathead, Montana 158% 112% 131%
Upper Clark Fork 231% 148% 170%
Bitterroot 128% 113% 121%
Lower Clark Fork 144% 107% 130%
Missouri 174% 95% 125%
Jefferson 161% 95% 126%
Madison 114% 111% 113%
Gallatin 123% 115% 120%
Headwaters Mainstem 135% 128% 132%
Smith-Judith-Musselshell 174% 117% 141%
Sun-Teton-Marias 141% 99% 123%
St. Mary 123% 119% 121%
Yellowstone River Basin 194% 83% 133%
Upper Yellowstone 194% 97% 147%
Lower Yellowstone 159% 83% 119%

Note: Streamflow forecasts are issued for multiple points on rivers and streams within a major river basin and are given as a range of exceedance probabilities. Consult the individual river basin of interest to see the range of values for streams of interest.

*Highest point forecast is the highest 50% forecast of all forecast points within the basin.

**Lowest point forecast is the lowest 50% forecast of all forecast points within the basin.

***Basin average forecast is an average of all 50% forecasts within the basin.