Roller balls are a sign that the surface of the snow is getting moist and weak. Photo: G. Antonioli Forecast link: GNFAC Avalanche Forecast for Wed Mar 15, 2017GNFAC Avalanche Advisory for Thu Mar 16, 2017GNFAC Avalanche Forecast for Fri Mar 17, 2017GNFAC Avalanche Forecast for Sat Mar 18, 2017GNFAC Avalanche Advisory for Sun Mar 19, 2017GNFAC Avalanche Forecast for Mon Mar 20, 2017Northern Gallatin, 2017-03-15Access other image sizes:Very Large 1200pxLarge 480pxMedium 220pxSmall 150pxOriginal