Friday, February 27, 2009

Forecasters warn of 'high' avalanche danger

Heavy snow, fierce winds lead to dangerous conditions in local mountains


By JASON KAUFFMAN
Express Staff Writer

After recent heavy snows and high winds, backcountry travelers need to be extra cautious when choosing routes across local mountain slopes, local avalanche forecasters warned Thursday.

"Selecting slopes with low 30-degree slope angles and not connected to anything steeper are today's travel recommendations," said Janet Kellam, director of the Sawtooth National Forest Avalanche Center.

Kellam's warning came during the midst of a strong winter weather system that slammed south-central Idaho early Thursday morning. The storm was expected to drop at least 7 inches of snow in the high mountains.

Packing strong winds from 15 to 30 miles per hour, the storm was expected to push the local avalanche danger even higher in the northern Wood River Valley, Sawtooth Mountains and mid to upper elevations.

"The avalanche danger will increase to high danger along any wind-loaded slopes in these locations as today's storm intensifies," Kellam wrote in her Thursday morning avalanche advisory.

The weather is expected to improve this morning. The National Weather Service is calling for partly sunny skies and a high near 34 degrees today.

Forecasters issued a hazardous weather outlook through last night for much of south-central and eastern Idaho, including the eastern Magic Valley, Sawtooth Mountains and Big and Little Wood river drainages.

According to Kellam, snowmobilers and skiers witnessed a number of slides in the mountains northwest of Ketchum on Wednesday.

"These were near Titus Peak, in the Headwaters-Frenchman's region of the Salmon River and the north side of Mushroom Ridge," she said. "All locations are where 1 to 2 feet of newer snow has accumulated or wind slabs have developed. One slide was approximately 300 feet wide and ran uphill on the other side of a narrow valley."

Kellam said Thursday's "hit and run storm" was forecast to bring rapid precipitation rates and strong southwest to northwest winds.

"In other words, we will see rapid loading on a snowpack that is already teetering on the brink of failure in many places," she warned. "Our northern sector and upper elevations with wind-loaded slopes have the greatest February snow load and it is already possible to trigger slides in these areas."

She said locals should expect the avalanche danger to increase in all locations on Thursday.

The recent slides reported by backcountry recreationists are running fast and fanning out wider than might have been expected due to the extent of the weak, underlying snow, Kellam added. She said most slides of the past several days have run on slopes with some portion steeper than 35 degrees, though one large avalanche was reported on a slope of less than that.

For today's complete avalanche forecast for the region, log on to the avalanche center's Web site at www.sawtoothavalanche.com.

Jason Kauffman: jkauffman@mtexpress.com




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