Powell, WY


Humidity: 21%

Wind: 7 mph

Higher Snowpack could mean flooding

Cool weather and precipitation over the past week have kept the snowpack in Wyoming well above average, and the Natural Resources Conservation Service has issued a high water notification for most of the state.

The snowpack in every basin in Wyoming increased last week, and the state’s average snowpack rose from 122 percent of average last week to 129 percent this week. A year ago, the average snowpack in the state was 77 percent of average.

Noting large increases in the snowpack around the state, Lee Hackleman, NRCS water supply specialist in Casper, said, “Due to cool temps and high snowpacks, there is a lot of water that will be coming down the mountains and into the rivers. We want to alert people around the state about these high volumes.”

Locally, according to this week’s Monday morning snow report, the snow water equivalent of the current snowpack in the Shoshone River Basin is 127 percent of average for this time of year. The level is up 6 percent from last week and 17 percent more than two weeks ago.

Hackleman said the current estimate is for 885,000 acre-feet of water, 131 percent of average, to flow into Buffalo Bill Reservoir during the May through July runoff period due to the high snowpack.

The reservoir can hold 646,565 acre-feet at capacity. Bureau of Reclamation officials have increased outflows from the reservoir in recent weeks, drawing it down to 58.5 percent of its capacity, or about 36.9 feet below its elevation when full. Officials are releasing more than 2,600 cubic feet per second this week in an effort to make room for the increased inflows.

Chris Jones at the National Weather Service in Riverton said the heavy snowpack raises the possibility of flooding when it begins to melt. Normally, that melting would already be in progress, but the recent weather has delayed it.

“Usually by now we see the snowpack starting to decrease, but we’re not seeing it yet,” Jones said. “It’s increasing instead.”

Jones said several days of temperatures in the 70s at lower elevations are necessary to begin the snowmelt, and those conditions aren’t in the three- to seven-day forecast. The concern is that, when the weather does warm, it will do so suddenly, and rapid melting will produce flooding.

“The later the cool weather goes, the more likely the warming will be sudden,” Jones said. “If it stays warm then, we could see flooding.”

The latest Weather Service bulletin on flood potential in the Shoshone River Basin estimates moderate potential for flooding in most of the basin, except for the extreme upper portions of the North Fork, where flood potential is rated moderate to high.

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