Ice storm warning
An Ice Storm Warning is issued by the National Weather Service of the United States when freezing rain produces a significant and possibly damaging accumulation of ice. The criteria for this warning vary from state to state, but typically an ice storm warning will be issued any time more than 1⁄4 inch (6.4 mm) of ice is expected to accumulate in an area; in some areas, the criterion is 1⁄2 inch (13 mm).
A freezing rain advisory or freezing drizzle advisory will be issued when a small amount of icing is possible.
In Canada, a Freezing Rain Warning has the same meaning.
...
Wikipedia