Flood Potential Tonight

Over the past couple days, isolated areas have received over 4" of rainfall. This has increased the flow of a few streams and rivers in the area. Here is a map of current stream flow across the region.




Areas marked by blue or black dots are probably dealing with the worst flooding right now. I'm expecting rain to persist through the night, so other locations could also experience flooding.

You can find the map above at this link:

http://water.usgs.gov/waterwatch/?m=real&r=va

Tornado Threat Has Diminished

Storms have weakened over the past couple hours, so the threat for tornadoes has diminished for Central Virginia. Rain is still likely tonight and will be heavy at times. We could easily pick up 1 to 3" of rain by tomorrow afternoon. For this reason, a Flood Watch has been issued for most of the area and is in effect until Friday afternoon.

Tornado Watch Until 8 PM

A Tornado Watch has been issued for the southern third of Virginia and is in effect until 8 PM. There is enough shear in the atmosphere that isolated weak tornadoes will be possible with the strongest storms this afternoon and evening.

Lightning Awareness & Safety

During strong to severe thunderstorms Wednesday, many of you heard the crashing thunder from frequent lightning strikes as these moved through Central Virginia (see Zach's blog entry below for a summary of the severe weather reports). As we all know, lightning is one of the most dangerous aspects of a thunderstorm. Sadly, a child playing catch Wednesday evening near a thunderstorm was struck directly by lightning and died. For those details, click here.

This is tragic, but you can stay safe during outdoor activities by knowing and adhering to basic lightning safety. The National Weather Service/FEMA/Red Cross have provided an online site with great lightning information. Here is a brochure for your family to read together. One fact I'd like to emphasize is that you do not have to be directly underneath where the rain is falling from a thunderstorm to be at risk of being struck by lightning. Lightning can strike as far out as ten miles from the rain! A handy trick to determine how far away a lightning strike is from you is to count the number of seconds from when you see the lightning strike until you hear the associated thunder. Divide that number by five, and that is an approximation of the miles between you and the strike. For example, if you count 25 seconds from seeing a strike and hearing the thunder, that strike was five miles away from you. This means you are in immediate danger and must seek shelter indoors and away from windows. Regardless of the distance, if you can hear thunder, you are close enough to be at risk; move indoors immediately.

Here is the list of cloud-to-ground flash densities ranked by state from 1996 to 2005. Virginia ranked 21st, with 8.6 flashes per square mile. Florida, as you might suspect, ranked number one with 26.3 flashes per square mile. Our neighbor to the south, North Carolina ranked 17th. West Virginia one-upped us and ranked 20th, Maryland was one behind us at 22nd.

Fast facts:

More people are hurt by lightning than by tornadoes or hurricanes.

Lightning bolts are five times hotter than the surface of the Sun!

One strike has between 100 million and 1 billion volts of electricity.

Wait at least 30 minutes after you hear the last roll of thunder before returning to your outdoor activities.

Lightning Myths