RICHMOND, Va. (AP) -- Gov. Bob McDonnell has declared a state of emergency in Virginia, as snow continues to pile up and knock out power to electric customers.

By issuing the declaration Wednesday, McDonnell authorizes state agencies to identify and position resources to respond rapidly to emergencies. That includes the Virginia National Guard, which has been authorized to bring up to 200 personnel for storm duty. Fifty soldiers have already been assigned to northern and central Virginia.

More than 1 foot of snow has piled up in Virginia's Shenandoah Valley as state police scramble to respond to hundreds of crashes and utility crews worked to restore power to more than 170,000 customers.

The wet, heavy snow is falling the hardest in the state's central and western regions.