Coming home from a fishing excursion on the Potomac River, a thunderstorm was rolling in. I noticed an unusally bright flash ahead of me to the right of the road, the light appeared to be much brighter and whiter than the lightening in the sky at the time. The light was stationary and flashing at regular intervals of approx. 2 to 3 seconds, it was flashing towards my car not in all directions. I could not see the object producing the light but there is no known source to my knowledge that would produce this light in this field.
I feel certain that this was not a known aircraft common to this area.