Snowbird snow-safety officials are working with the U.S. Forest Service and the Salt Lake County Sheriff's Office to determine more precisely what caused an in-resort avalanche Sunday that killed a 27-year-old skier.

Sheriff's spokesman Shane Manwaring said "we're weeks away from any conclusions" about the conditions in which Heather Gross died Sunday after being buried for nearly an hour by a slide in the Eye of the Needle area partway down Mount Baldy.

A Utah Avalanche Center forecaster was evaluating the snowpack on the expert slope where the avalanche slab broke loose, said Forest Service snow ranger Steve Scheid, while GPS coordinating equipment was pinpointing the location to determine if the slide took place on private Snowbird land or on land leased from the Forest Service. The distinction clarifies whether the Sheriff's Office or the Forest Service has primacy in the investigation, which Scheid called a cooperative effort of all three organizations.

"The avalanche control community in the Cottonwood canyons is close-knit. They communicate and, when something like this happens, this community rallies as one to work together to try to save lives," he said Monday.

Investigators will review the control work that Snowbird Ski & Summer Resort did earlier that morning on the steep slopes leading down Mount Baldy into Peruvian Gulch, a powder playhouse that had opened for the first time this season with the arrival of the weekend storm.

"We'll see if they were following the standard procedures on their [avalanche control] operating plan," Scheid said, describing Snowbird's snow safety team as "leaders. They invented this control stuff. They've been very open and cooperative, trying to understand the best we can what caused this."

Snowbird spokesman Jared Ishkanian said the resort did not make any changes to its control plan Monday, "in terms of snow safety or ski patrol," and was focusing on assisting the Gross family and the many Snowbird people who knew the victim, a lifelong season pass holder who graduated from Brighton High School and was a graduate student in linguistics at the University of Utah.

"It's pretty evident Heather had some pretty close connections to Snowbird," he said. "We're doing all we can to reach out to the family -- and to comfort the Snowbird family. It's definitely a tragedy that was felt really strongly among our community here."

Gross is the second woman killed by an avalanche while skiing inbounds in the past half century, according to National Weather Service statistics. Slides within resort boundaries have claimed seven lives overall within that time span, the last being a 30-year-old Colorado man buried in a Dec. 23, 2007 avalanche at The Canyons. The next most recent in-bounds fatality was a 16-year-old Massachusetts boy who died Feb. 19, 1986 in a slide at Alta's Devil's Elbow. Snowbird's only other fatality occurred March 3, 1977.

"Inbounds avalanche fatalities are quite rare," said Bruce Tremper, Utah Avalanche Center director and author of the book Staying Alive in Avalanche Terrain.

But early-season fatalities are not uncommon. Last winter, three deaths occurred between Dec. 23 and Dec. 31. In 2004, one person was killed Dec. 10, three others the next day.

That's because early season weather doldrums often create thin layers of old snow that suddenly get buried beneath a blanket of new snow. The transition zone can be slippery.

"Thin snow means weak snow," said Tremper. "When you put a load of new snow on top of that, you are overloading those weak layers. So it can be sensitive and tricky."

Utah averages about four avalanche fatalities per year, according to the center.

Current avalanche danger, rated "considerable" along the central Wasatch Front, is likely to intensify as more storms are predicted for this week. Upper elevation ridges on steep slopes facing northwest to east are most susceptible.

Forecasts are available at http://utahavalanchecenter.org.

mikeg@sltrib.com

wharton@sltrib.com

Correction: This is a corrected version of a story that ran in Tuesday's Tribune. Heather Gross, who was killed Dec. 14 in an avalanche at Snowbird, was the second woman killed in an inbounds ski resort area avalanche. Another female skier died at Park City on March 19, 1985. The printed story omitted the Park City death.