More Severe Weather Likely This Afternoon. A Tornado Watch until 8pm

**Update** A TORNADO WATCH Has been issued for a good portion of the viewing area until 8pm. This means that conditions are favorable for tornadoes this afternoon and evening. We are currently watching a line of storms in Central TN moving east. These storms have a history of warnings.  Click here for more:

Now for round two this afternoon, and possibly the best chance for severe weather this season. The Storm Prediction Center has put the entire TN Valley under its first “Moderate” risk for severe storms. All modes of severe weather are possible, including tornadoes. Note the risk areas below. Click on the maps for more information.

Severe Risk                                                        Tornado Risk

Large Hail                                                            Damaging Winds

Here is the synopsis with a little meteorology jargon mixed in. An area of low pressure is currently moving into West KY this morning with a warm front well north and a cold front to the west. This puts our area in the “Warm Sector” meaning the MOST unstable part of the storm. Unlike the last few times, there are no storms along the coast that would rob our  moisture and influx of warm air. I am looking for thunderstorms to continue into the mid to late afternoon hours as they race quickly to the east and northeast. Here are some of the parameters we are looking at, especially with the midday sunshine expected:

1. Dew points (moisture): 50-60 degrees: “Semi-juicy”
2. Cape (Energy): 1200-1800 J/KG: “Moderate-High” means storms will build vertically very quickly.
3. Sufficient vertical and directional shear: Vertical Shear (winds increase with height) will “tilt” storms keeping the updrafts from being cut off by the downdrafts. Directional Shear (winds change direction with height) causes updrafts to rotate and storms to rotate, which could lead to tornadoes.
4. Very Cold 500mb Temps: Cold temps aloft will allow the warm air to rise and will help with hail development.
5. Jet Stream Support. The Low Level Jet is pumping in the warm moist air from the south, while the Jet Stream around 35,000 feet is diverging aloft helping to pull the warm air up, leading to stronger storms.

While these ingredients are certainly not the highest we have seen around here, they are sufficient enough to produce super cells this afternoon and evening. Unlike a line of storms in previous cases, we are looking for more individual storms, which could rotate and lead to large hail, damaging winds and isolated tornadoes. Unfortunately, the tornado threat today is the highest it’s been in a while. This is a good reminder that having a weather radio is vital. The storms should end later this evening and will be gone before midnight. I expect at least a watch to be issued this afternoon while the Storm Team 12 meteorologists follow the warnings.

Patrick could be very busy at 6pm tonight and before!

Stay safe this evening, but if you have any reports or pictures you can send them to pictures@wdef.com and follow reports using twitter @wdefbrian and @wdefnews12.

See you soon,

Brian