This generally means... snowfall accumulating to 4" or more in depth in 12 hours or less; or snowfall accumulating to 6" or more in depth in 24 hours or less In forecasts, snowfall amounts are expressed as a range of values, e.g., "8 to 12 inches." However, in heavy snow situations where there is considerable uncertainty concerning the range of values, more appropriate phrases are used, such as "...up to 12 inches..." or alternatively "...8 inches or more...".

snowfall that reduces visibility to 0.31 mile (0.5 kilometer) and yields, on average, 4 inches (10 centimeters) or more in a twelve-hour period or 6 inches (15 centimeters) or more in a twenty-four-hour period.

usually means snowfall of four air inches or more in twelve hours or less, or six inches or more in twenty-four hours or less in lower elevation; in higher elevations it means twelve inches or more in twelve hours or less, or eighteen inches or more in twenty-four hours or less.