Snowpack in the mountainous areas that feed the Missouri and Yellowstone river basins are setting some records, and that could mean some flooding is likely to occur in the Williston area, once all that snow begins to melt in May and June.
Ten SNOpack TElemetry (SNOTEL) locations that feed the Upper Yellowstone, Upper Clark fork and Missouri Mainstem RIver basins are the highest on record for April 1, according to USDA’s National Resource Conservation Service, and 12 locations are the second highest on record.
The exceedance forecast for the Missouri River basin is 95 to 174 percent of normal and 83 to 194 percent for the Yellowstone. Both basins are carrying around 134 percent of the normal snow water equivalent, which measures how much actual water is in the snow pack.
The National Weather Service’s Climate Prediction Center is predicting above average precipitation and below average temperatures through the end of April. The long-duration streamflow forecasts for April 1 through July 31 are above average for most stream gages in Montana, and could approach record levels this spring and summer at Belfry, Montana, which is near Clark’s Fork of the Yellowstone.
Snowpack in the mountains is approaching 2011 levels. That could bring back some bad memories for some, according to Alan Schlag, hydrologist for the National Weather Service in Bismarck, but it’s not as bad as it may sound to those who remember 2011 flooding.
“The reality we have to remember is that in 2011 we had an incredible rain event on the Plains that coincided not just with heavy mountain snowpack, but also with above average snowpack in Montana and North Dakota,” he said. “Usually plains snowpack isn’t that big a deal, but that year it was.”
Lucas Zukiewicz, water supply specialist for Montana, said most areas of Montana are also still below the snowpack levels of 2011.
Schlag said they are in North Dakota as well, thanks to warm periods in both December and January that removed a substantial amount of accumulating snowpack, helping to keep things in check.
“It’s really only been in the last few weeks that we caught up with a semblance of normal snowpack,” Schlag said.
As it stands, Schlag expects to see at least some flooding in the Williston area when the snowpack melts, but how much will depend on exactly what happens weatherwise in April, May and June.
NRCS will publish an updated report in May that will help water users prepare for runoff this spring and summer. Outlook reports are located at https://www.nrcs.usda.gov/wps/portal/nrcs/mt/snow/waterproducts/basin/.
“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.”