Winter storm warning begins at 9 p.m.
Earlier forecasts had said Loudoun could start seeing rain as early as 1 p.m. that would later develop into a mix of snow.
The latest forecast is calling for a rain and snow mix to begin around 4 p.m. today.
When it's all said and done, Loudoun County – in a worst case scenario – could see as much as 18 inches of snow by Thursday morning, according to Calvin Meadows, meteorological technician with the National Weather Service.
The higher elevations along the Blue Ridge Mountains could see as much as 21 inches of snow.
Residents will not likely start to see significant accumulation until after 2 a.m. Wednesday when the temperature drops below freezing, Meadows said.
An accumulation of 3 to 5 inches of snow is expected overnight, he said.
"During the heart of the storm snow could fall at such a rate that it could start accumulating on the roads," Meadows said.
The area east of the Blue Ridge Mountains to Interstate 95 will waver between rain and snow throughout the storm.
"We have low confidence for snow fall totals in that area because of where the rain/snow line is going to fall," Meadows said. "We will be updating the forecast as we get closer to the event … Right now the storm hasn't fully developed yet."
The storm's low pressure center is currently over northern Mississippi, he said, so Loudoun has "a ways to go before it really gets to our area."
In anticipation of the storm, the Loudoun County Sheriff's Office is urging motorists to be prepared and make sure their vehicles are equipped with a well-stocked winter driving kit.
The office is also asking residents to stay off the roads during the storm unless travel is necessary.
To keep up with current road conditions visit http://511virginia.org/Default.aspx; for statewide highway information 24-hours-a-day, call the Highway Helpline at 1-800-367-ROAD or check local traffic incident information at http://sheriff.loudoun.gov/traffic.