The funnel cloud need not be visibly touching the ground for a tornado to be on the ground. Look for rotating debris rising up from the ground. While it is best to have the report close to the event so we can use the information to assist us with issuing warning, the damage report is also important for publishing storm data and research purposes. Therefore, we want this information regardless of how old it might be. Flash flooding can be a very localized event occurring from one thunderstorm.
Flash flooding can also occur when a dam suddenly breaks.
The dam may be manmade, or it could be an ice jam or a debris dam that backs up water and then suddenly lets loose. Because it takes time for the rain to run into the small streams and then into the rivers. River flooding often occurs after the rain has stopped. People along the lower stems of the large rivers such as the Potomac and Rappahannock, may not see the flood waters until 1 to 2 days after the rain has stopped. Tidal flooding can occur in the tidal portions of the rivers such as the Potomac up into Alexandria and Washington, DC or the Rappahannock up into Fredericksburg.