12/1/2022
State Highway 21 from Grandjean to Banner Summit closed due to avalanche risk
LOWMAN -- The Idaho Transportation Department (ITD) has closed State Highway 21 from Grandjean to Banner Summit due to high avalanche risk.
ITD’s Avalanche Crew of forecasters will continue to monitor the snowpack and temperature north of Lowman. The highway will reopen when the snowpack has stabilized and the risk of active avalanches is reduced.
The alternate route between the Treasure Valley and the Stanley area is to travel east on Interstate 84, exit in Mountain Home at Exit 95 to U.S. Highway 20, then head north on State Highway 75.
The ITD Avalanche Crew monitors the snowpack along this section of highway daily in order to forecast the risk of avalanches large enough to reach the roadway. This practice allows ITD to keep the highway open during the winter months with a reasonable confidence of safety for the traveling public.
There are sixty regular avalanche paths in this 11-mile stretch of SH-21. Avalanches can be triggered without warning. For this reason, there is no parking or stopping within this section of road during the winter.
Updates on closures and openings will be posted on 511.idaho.gov. Future closures will be announced on Idaho 511 and ITD's Twitter account.