There are three different types of frozen precipitation. The phase of precipitation that makes it to the ground depends on the temperature profile through the atmosphere. If the temperature stays above freezing all the way down, then the precipitation will fall as snow. If there is a warm layer in the atmosphere that melts the snow before it reaches another cold layer closer to the ground to start refreezing, then it will fall as sleet. If there is a thicker warm layer in the atmosphere, the precipitation will melt to rain, and then refreeze as it hits the below 32 degree cold layer. In this case it will be freezing rain.
WX 101 for Flash Flooding.
WX 101 for Winter Weather Advisories, Watches, and Warnings.
WX 101 for Severe Weather Categories.