SHERIDAN — Statewide, precipitation in January was nearly 115 percent of average and mountain snowpack is at approximately 120 to 135 percent, meaning near normal snowmelt streamflow volumes are expected across most the major basins in Wyoming.
The Upper Tongue River Watershed, which encompasses Sheridan County, is above the state average for snowpack and precipitation. Wyoming National Oceanic and Atmospheric Administration Hydrologist Jim Fahey said, to date, the Upper Tongue Watershed was at 126 percent of normal for snowpack. Through January, precipitation was at 135 percent.
“We had a wet fall, so that’s carried us over a bit,” Fahey said. “I like the fact that we started out pretty good, that we were pretty wet there in the fall. It looks good for runoff.”
Snowpack water numbers are highest across northeast Wyoming.
Several factors affect runoff in the spring, which impacts the likelihood of a good or bad fire year, but having above average snowpack and precipitation bodes well when the region’s wettest months typically occur in April, May and June, Fahey said.
Fahey said it’s too early to tell if flooding may be a problem.
In surrounding watersheds, precipitation levels are also above average. The Powder River Basin to the southeast is at 145-150 percent of normal and is expected to have above average streamflow volumes.
The Big Horn Basin is at 145 percent of normal precipitation.
Fahey said there is a theory that runoff is good in years with a wet fall because soil moisture stays high and freezes over the winter. When spring rains and snowmelt begin to occur, runoff is good because the ground is already saturated and does not absorb much moisture. He said the state would need additional soil moisture monitors to adequately test this theory, but that it makes sense hydrologically.
Fahey added that wind can have a significant impact on snowmelt and runoff. If snowpack levels drop below 90 percent, the soil is more likely to dry out quickly in high winds.
Precipitation was highest in the Crow/Lodgepole Creek Drainages in southeast Wyoming at 188 percent of normal and lowest, at 77 percent, in the Upper Bear Basin in southwest Wyoming.
Reservoirs storages across Wyoming are slightly below average for February, but Fahey expects the higher snowpack and precipitation levels to correspond with above average reservoir storages.