The National Weather Service uses the following definitions when describing winter weather:
An advance statement that severe winter weather conditions are possible within the next day or two.
An urgent statement that severe winter weather conditions have begun or will begin within about 12 hours.
A statement that winter weather conditions are imminent or occurring. These conditions will cause significant inconvenience, and may become hazardous or life-threatening if safety tips are not followed.
Snowfall which accumulates to a depth of at least 4 inches in 12 hours or 6 inches in 24 hours.
Pellets of ice composed of frozen or mostly frozen raindrops, or snowflakes which have melted and refrozen.
Freezing Rain/Freezing Drizzle
Rain or drizzle which falls as liquid then freezes when it strikes the ground or other surface.
The formation of thin ice crystals on the ground or other surfaces.
A cooling effect caused when wind blows across exposed skin.