The Idaho Transportation Department will be closing Idaho Highway 21 from Grandjean to Banner Summit tonight due to a high avalanche risk.
A weather system bringing rain and snow is likely to trigger avalanches in this section of highway. The anticipated closure will begin at 6 p.m. on December 20. However, actual weather impacts may require an earlier closure. Motorists needing to use the roadway are advised to make the trip immediately or plan to use alternate routes.
The alternate route between the Treasure Valley and Stanley area is to travel east on I-84, exit in Mountain Home at Exit 95 to U.S. 20, then head north on Idaho Highway 75.
The ITD Avalanche Crew monitors the snowpack along this section of highway in order to forecast the risk of avalanches large enough to reach the roadway. This practice allows the Department to keep the highway open during the winter months with a reasonable confidence of safety for the traveling public. Previously, the Department closed this section of highway after the first avalanches hit the road.
The Avalanche Crew will continue to monitor the snowpack as a snowstorm hits the area and after. The highway will reopen when the snowpack has stabilized and the risk of active avalanches is reduced. Updates on closures and openings will be posted on 511. Future closures will be announced on 511 and ITD’s Twitter account.
There are sixty regular avalanche paths in this 11-mile stretch of ID-21. Avalanches can be triggered without warning. For this reason, there is no parking or stopping within this section of road during the winter.
Below is a gallery of activities the Avalanche Crew performs during the winter.
