chuck harry forgot the bottom half of that chart.
AVALANCHE SAFETY BASICS
Avalanches don't happen by accident, and most human involvement is a matter of choice, not chance. Most avalanche accidents are caused by slab avalanches which are triggered by the victim or a member of the victim's party. However, any avalanche may cause injury or death and even small slides may be dangerous. Hence, always practice safe route finding skills, be aware of changing conditions, and carry avalanche rescue gear. Learn and apply avalanche terrain analysis and snow stability evaluation techniques to help minimize your risk. Remember that avalanche danger rating levels are only general guidelines. Distinctions between geographic areas, elevations, slope aspects and slope angles are approximate and transition zones between dangers exist. No matter what the current avalanche danger there are avalanche-safe areas in the mountains.