Higher temps pose snowmelt flooding risk

WORLAND – After a week of warm weather, area creeks and rivers have experienced a noticeable rise, as snow at higher elevations begins to melt. At the same time, the National Oceanic and Atmospheric Administration (NOAA) in Riverton reports that while precipitation is above average, snowmelt streamflow volumes are expected near normal.

According to a recent flood threat assessment compiled by the state, the snow-to-water equivalent is down to 115 percent of normal this year, as compared to 139 percent a year ago.

According to a Thursday report released by the NOAA, “April 2018 precipitation totals across Wyoming were 95 to 105 percent of average. Precipitation numbers varied between 171 percent of normal over the Snake River Drainage (western Wyoming) to near 65 percent of average over the Laramie River Basin (southeastern Wyoming).

“Mountain snowpack across Wyoming remained at 105 to 115 percent of median by early May. Snowpack water numbers continue to be the highest across basins in northwest to north central Wyoming—varying between 120 to 160 percent of median. Totals across basins in southern Wyoming were at 65 to 90 percent of median. 

“Overall, near normal (95 to 105 percent) snowmelt streamflow volumes are still expected across Wyoming during the upcoming snowmelt runoff season. Above average streamflow volumes are forecasted across portions of the Wind, Shoshone, Snake, and Upper Yellowstone Watersheds. The Tongue, Lower Green, Upper North Platte and Little Snake Basins are still expected to have below normal streamflow volumes during the upcoming snowmelt runoff season.”

A report released by the Bureau of Reclamation, also on Thursday, forecasted runoff totals for the following area through July:

Bighorn Lake – Big Horn River April through July inflow to Bighorn Lake is forecast to be 1,740,500 acre feet (af), which is 149 percent of the 30 year average of 1,165,700 af. Approximately 391,200 af of the forecast volume was accumulated during April, which is 243 percent of the April average.

Buffalo Bill Reservoir – Shoshone River April through July inflow to Buffalo Bill Reservoir forecast has been increased to 1,100,000 af, which is 156 percent of the 30-year average of 704,400 af. Approximately 76,525 af of the forecast volume was accumulated during April, which is 167 percent of the April average.

Boysen Reservoir – Wind River April through July inflow to Boysen Reservoir forecast has been lowered to 750,000 af, which is 130 percent of the 30-year average of 577,700 af. Approximately 62,181 af of the forecast

volume was accumulated during April, which is 127 percent of the April average.

Bull Lake Reservoir – April through July inflow to Bull Lake Reservoir from Bull Lake Creek forecast has been lowered to 160,000 af, which is 114 percent of the 30-year average of 140,400 af. Approximately 5,647 af of the forecast volume was accumulated during April, which is 134 percent of the April average.

Wind River – April through July snowmelt runoff into the Wind River above Bull Lake Creek forecast has been lowered to 550,000 af, which is 132 percent of the 30-year average of 416,300 af. Approximately 38,299 af of the forecast volume was accumulated during April, which is 154 percent of the April average.

As of Thursday, local totals for area creeks and rivers included Ten Sleep Creek at Ten Sleep at 2.82 feet, with a flood stage of 4.5 feet, the Big Horn River at Worland at 5.45 feet with a 10.5 foot flood stage, Big Horn River at Basin at 5.54, also with a flood stage of 10 feet, the Shoshone River at Lovell at 7.75 with a flood stage of 11 feet and the Wind River at Riverton at 6.41 feet with a flood stage of only 9 feet.