A moderate (G2) to strong (G3) geomagnetic storm is in progress at high latitudes. Basically, there is a decent stream of particles from the sun that is interacting with the Earth's magnetic field causing visible auroras.
In cases like this, it's even possible that we could see the the Northern Lights across parts of northern Maryland and northern Virginia.
As for when to see them...that's much harder to predict. The Northern lights can be visible at any time of day. They have been observed in arctic areas as early as 4 PM and as late as 6 AM. The best time to see them seems to be around 9.30 PM to 1 AM.
Here's a great website to learn more and track Auroras. http://www.aurora-service.org/aurora-forecast/.
Another good website to check is http://www.spaceweather.com/.
We'll have clear skies, so if the Northern Lights are out there, we'll see them.