A pair of snowboarders kicked off a rare event in Steamboat Springs on Wednesday afternoon. Call it an urban avalanche.
"It happened so quickly," John St. John said. "It didn't hesitate, and it came in a big way. Right there in the middle of town."
St. John and fellow snowboarder Eugene Buchanan triggered the slide between 2:30 and 3 p.m. Wednesday. Neither man was caught in the avalanche or injured.
The small avalanche ran about 120 feet down a steep slope on the western edge of the Howelsen Hill area. The ridge where the avalanche occurred is between Fairview and the Yampa River. It can be easily seen from the corner of 12th and Yampa streets.
Rain that changed to heavy snow overnight Tuesday into Wednesday may have played a role in the instability of the snowpack.
Local avalanche expert Art Judson described it as a wet slab and estimated the snow fell 60 vertical feet on a slope, approaching 35 degrees at the trigger point.
"Snow conditions causing the instability would be thaw leading to weak, cohesion-less grains containing some free water," Judson said. "In a word, the snow was rotten."
Buchanan and St. John confirmed Judson's analysis.
"We knew the snow was rotten, but we certainly didn't expect it to slide," Buchanan said.
St. John said he had the impression that there were no layers in the snowpack. Instead, the snow on the steep slope was uniformly mushy from the surface to the ground.
Ethan Greene with the Colorado Avalanche Infor--mation Center said Wednesday's avalanche in Steamboat illustrates how high temperatures this week "wreaked havoc on a fairly stable snowpack and produced a significant wet slide cycle."
"Nighttime temperatures have been dropping below freezing the last two nights, and we should have a good freeze again (Thursday night)," Greene said. "However, heat has penetrated deep into the snowpack, especially below tree line."
The snow that fell earlier this week is helping to insulate the snowpack, he added. Greene advised that if skiers and riders in the backcountry find themselves breaking through the surface into mushy snow, they should stay away from steep slopes.
Buchanan and St. John have formed a midday habit of looking for a little powder during the lunch hour. They ski or snowboard on small slopes they describe as "dorky lines."
They knew in advance that the wet snow Wednesday wouldn't support skis, so they opted for the broad surface of their snowboards. They first attempted to ride a slope above 13th Street (Twentymile Road) on the backside of the steep ridge where the avalanche occurred.
The snow was so "punchy" that Buchanan said the slope wasn't worth riding. They then scouted the steep slope on the south side of the Yampa River from 12th Street. They decided to give it a try, and as they came over the top of the ridge, Buchanan said they checked their speed. As Buchanan came around a small fir tree, the slope let loose.
"It went, but it all went below me," Buchanan said.
The avalanche fracture ran to the ground, but there was enough snow remaining on the slope that the two men could ride out the path and head back to their vehicle via Howelsen Hill.
"There was a lot of snow at the bottom," St. John said. "It created a nice little debris pile."
Judson rated the size of the avalanche as a "one" on a scale of five. The fracture line was not smooth, Judson observed, indicating that cohesion among the grains of snow was low. There also were signs that the snow might have been creeping or gliding on the surface of the ground before the release.
St. John and Buchanan have had previous experience with avalanches, but they stressed that they don't take a reckless approach to skiing and riding outside ski areas.
St. John witnessed slide activity in the mountains surrounding Jackson, Wyo., while living there, and once was covered up to his knees in wet, cement-like snow produced by a small avalanche.
Buchanan said he was buried in a slide on Feb. 14, 1987 while cross-country skiing near Telluride with friends.
"I hit a tree with my forearm and was able to grab it," he recalled.
Buchanan tucked behind the tree to get some relief from the avalanche and formed an air pocket that allowed him to breathe even though he was buried. Friends dug him out.
Since then, he said, he has taken a number of avalanche safety courses and always takes a transceiver, probes and shovel with him into the backcountry.
St. John said he is revising his plans to ski in the backcountry this weekend, and he urges others to do the same.
-- To reach Tom Ross call 871-4205
or e-mail firstname.lastname@example.org