Yellowstone Snowpack Update

Here at Sweaty Waders we are all watching with great interest how this years massive snowpack will effect the Yellowstone River this summer.    Sweaty Waders and the Yellowstone River Report will keep you posted over the next month.  Our first installation of the Yellowstone Snowpack Update is an article from the Billings Gazette.

Big, late snowpack ready to melt

Snowpack in the mountains that feed the upper Yellowstone River basin on Tuesday held more water for this late in the year than any other year in recorded history.

Thanks to this week’s soggy storm system, 2011 surpassed 1997, the last major flood year in the basin, said Brian Domonkos, water supply specialist for the Natural Resources Conservation Service. The storm added as much as 1.6 inches of meltwater in some places, he said.

Overall snowpack is still not as high as the all-time deepest pack in 1997, he said, but the melt started a little earlier that year.

Meltwater this year is finally ready to come out, three to four weeks after it normally begins hitting Montana rivers and streams.

“It started to melt May 2 on the upper Yellowstone,” Domonkos said.

But a return of freezing temperatures above 7,000 feet halted the process. It is expected to regain momentum as temperatures warm this week, said Joe Lester, meteorologist with the National Weather Service in Billings.

“We need it to melt,” Lester said. “The longer it stays on, the more problems we have.”

Warming will be moderate — 60s and 70s at lower elevations — meaning it will probably still freeze at night at higher elevations, he said. That could make for a nonthreatening, gradual melt.

“The worst case would be a lot of rain on the snow,” he said. “We’re not seeing that in the forecast. Or warming up really fast. I don’t see us warming up to the 80s and 90s, which sometimes happens this time of year.”

Domonkos said snowpack began turning statewide on Thursday. That’s the point when it reached the isothermal stage, meaning that the pack had achieved a uniform temperature in preparation for melting.

Normally, the pack starts melting first on the west side of the state, but this year the Yellowstone’s pack — late as it was — began melting a few days earlier.

Before the recent storm shut off the spigot, about 1.5 inches of meltwater had come down from the upper Yellowstone basin. Another 25.5 inches remains, Domonkos said. The upper Yellowstone is the stretch of river between Yellowstone National Park and Custer. About 5 percent of the meltwater in the lower Yellowstone basin melted during the same time.

The Musselshell basin lost about 1.5 inches, or 11 percent, of the 14 inches of meltwater holed up in the pack.

Earlier this month, NRCS released its May-through-July streamflow forecast, predicting streamflows statewide at 149 percent of average — 154 percent west of the Divide and 146 percent east of the Divide.

Forecast for the upper Yellowstone was 142 percent of average, and the lower Yellowstone was forecast at 138 percent of average.

The Smith-Judith-Musselshell was forecast for 178 percent of average.

Snowpack in some areas Tuesday stood at more than twice average amounts for this time of year. Domonkos said those figures were high partly because the snow has hung on so late in the spring. They do not reflect peak seasonal snowpack.

The upper Yellowstone, for instance, had 158 percent of its normal snowpack for May 10, but the basin’s peak snowpack for the season was 138 percent of its average peak.


1 Comment so far

FYI…The Bighorn river was even blown out today! Mud,mud,muddy! All trips cancelled…

I hear that the spring creeks are clear:)

Your biased friend,
Bradley

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