Spring has Sprung in Montana Melting Low Elevation Snowpack, High Elevation Snowpack Holding Strong

Spring has Sprung in Montana Melting Low Elevation Snowpack, High Elevation Snowpack Holding Strong

Source: NRCS
Click here to read the article: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/mt/newsroom/releases/?cid=NRCSEPRD1323671

Lucas Zukiewicz

FOR IMMEDIATE RELEASE

BOZEMAN, Mont., April 7, 2017 – March started off with a bang across Montana, dropping snow in all river basins for the first week and a half, increasing already good snowpack totals from March 1, according to snowpack data collected by the USDA Natural Resources Conservation Service, Montana.p>

However, as spring arrived the weather patterns quickly changed and sunny days with well above average temperatures persisted until the end of the month. Valley snowcover lingering at the beginning of March quickly melted, and low elevation SNOTEL (SNOpack TELemetry) sites saw a transition to a spring snowpack structure that is primed to melt. During the third week of the month, temperatures struggled to get below freezing overnight at low elevation measurement locations, beginning the spring melt of the snowpack.

“Fortunately, this melt was primarily confined to elevations below 6000 feet west of the Divide and 7000 feet east of the Divide,” Zukiewicz said. &ldquoThe mid to high elevation locations experienced little, if any, melt during this time and remain in good shape for April 1.”

West of the Divide, most river basins experienced a gain in snowpack percentages from March 1, while basins east of the Divide have dropped from last month. The drops are a direct result of the the early snowmelt, coupled with the lack of snowfall during the latter half of the month.

Even though March didn’t bring ample snowfall to some parts of the state, early season snowfall during winter and excellent totals in most basins on March 1 has resulted in most basins across the state having near to above normal snowpack for April 1. Only a few basins across the state are below normal for April 1, according to Zukiewicz.

Basins along and east of the Divide in southern and central Montana are currently the lowest in the state for snowpack on April 1. The Upper Clark Fork and Gallatin River basin experienced decreases during the month and are below normal for snowpack totals for this date. The combined Smith-Judith-Musselshell River basin, which has been well below normal throughout the winter, is well below normal and the loss of low elevation snowcover did not help the situation this month.

The low elevation melt in the southern half of the state, and rain in the northwest, caused increases in streamflows during the month. Some minor flooding did occur on small streams, but the bulk of the water contained in the snowpack at mid and high elevations still remains to move into the river systems. Streamflow forecasts are mostly near to above average for the April 1 – July 31 time period, but some forecasts for some rivers are below average due to the lack of snowpack on April 1. Because forecasts can vary widely within a major river basin, water users should view forecasts for individual rivers by reading the monthly water supply outlook report for their basin, said Zukiewicz.

Monthly Water Supply Outlook Reports can be found here after the 5th business day of the month: http://www.nrcs.usda.gov/wps/portal/nrcs/main/mt/snow/waterproducts/basin/

April 1, 2017 Snow Water Equivalent

River Basin Percent of Normal Percent of Last Year
Columbia River Basin 102 107
 – Kootenai in Montana 105 112
 – Flathead in Montana 105 109
 – Upper Clark Fork 93 98
 – Bitterroot 105 108
 – Lower Clark Fork 106 116
Missouri River Basin 92 94
 – Jefferson 100 90
 – Madison 104 104
 – Gallatin 87 88
 – Headwaters Mainstem 92 89
 – Smith-Judith-Musselshell 70 64
 – Sun-Teton-Marias 116 178
 – St. Mary-Milk 92 131
Yellowstone River Basin 132 142
 – Upper Yellowstone 117 126
 – Lower Yellowstone 145 154
West of the Divide 102 107
East of the Divide 112 118
Montana Statewide 100 104

April 1, 2017 Precipitation

River Basin Monthly Percent of Average Water Year Percent of Average Water Year Percent of Last Year
Columbia River Basin 187 130 124
 – Kootenai in Montana 191 138 119
 – Flathead in Montana 191 135 127
 – Upper Clark Fork 148 115 119
 – Bitterroot 198 120 120
 – Lower Clark Fork 214 137 129
Missouri River Basin 113 129 128
 – Jefferson 110 119 116
 – Madison 127 141 140
 – Gallatin 117 127 117
 – Headwaters-Mainstem 96 114 114
 – Smith-Judith-Musselshell 89 108 101
 – Sun-Teton-Marias 162 129 161
 – St. Mary-Milk 149 157 140
Yellowstone River Basin 167 150 156
 – Upper Yellowstone 151 147 147
 – Lower Yellowstone 179 155 165
West of the Divide 187 130 124
East of the Divide 140 137 140
Montana Statewide 154 133 129

April-July 50% Exceedance Forecasts

River Basin Highest Point Forecast* Lowest Point Forecast** Basin Avg Forecast***
Columbia 153% 97% 113%
Kootenai, Montana 137% 107% 124%
Flathead, Montana 153% 104% 120%
Upper Clark Fork 111% 97% 103%
Bitterroot 110% 101% 107%
Lower Clark Fork 117% 109% 112%
Missouri 117% 62% 97%
Jefferson 116% 73% 93%
Madison 108% 97% 102%
Gallatin 93% 82% 88%
Headwaters Mainstem 101% 93% 97%
Smith-Judith-Musselshell 80% 62% 73%
Sun-Teton-Marias 117% 94% 113%
St. Mary 117% 115% 116%
Yellowstone River Basin 222% 76% 127%
Upper Yellowstone 158% 76% 120%
Lower Yellowstone 222% 102% 134%

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.