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BOISE -- A 12-mile stretch of Highway 21 between Grandjean Junction and Banner Summit closed this afternoon as a precaution due to recent snowfall.

The Idaho Transportation Department closed the highway to travelers at 4 p.m. Friday.

The mountainous roadway, popularly known as Avalanche Alley, includes about 60 avalanche pathways that cause 90 percent of Idaho avalanches that affect highways. More than 250 inches of snow typically fall here every winter.

The first avalanche closure last year was Dec. 16.

ITD says its forecast team has reduced closures by more than 60 percent since it began forecasting slides and slide threats three years ago. Roughly 45 to 50 slides happen in the area each winter season.

The decision to close the roadway is based on forecast conditions, and the likelihood of receiving more snow in the coming days, according to ITD communication specialist Mel Coulter.

Forecasters say the avalanche danger is considerable.

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