Here are the definitions of the advisories.
Level 1 - Roadways are hazardous due to accumulated snow or ice. Drive cautiously.
Level 2 - Roadways are hazardous due to blowing and drifting snow and/or ice cover. Only those who believe it is necessary to drive should be on the roadways. Contact your employer to determine if you should report to work.
Level 3 - Roadways are closed to all non-emergency travel due to extremely hazardous conditions. No one should be on the roadway unless it is absolutely essential to travel. Those operating vehicles on the roadway for non-emergency reasons may be subject to arrest.