Gov. Bob McDonnell issued a state of emergency in the commonwealth early Wednesday, authorizing state agencies to aid local governments in combating the harmful impact of this early-March snowstorm.

Certain parts of the state have seen more than 12 inches of snow, while estimates in Loudoun range from 4-8 inches.

More than 300,000 Virginians were without power as of noon Wednesday, according to the governor's office, which cautioned that more power outages are likely as the day and storm wears on.

The state of emergency allows state agencies to position resources for quick responses throughout the state. Virginia State Police have responded to more than 1,300 calls since late Tuesday night.

Northern Virginia has been somewhat spared from a large number of incidents. In Prince William, Loudoun, Arlington and Fairfax Counties and Alexandria there have been 13 reported crashes, 52 disabled vehicles and 192 calls for service.

Locally, consistent snow is expected through the afternoon, potentially dying down around 5 p.m.

The Loudoun County Sheriff's Office is cautioning motorists to stay off the roads unless driving is absolutely necessary.