We are still on track to see some strong and severe thunderstorms later this afternoon lasting through this evening through about 10:00 PM to Midnight.
RIGHT NOW: As I write this about 8:00 AM, the Low Pressure is centered North of Nashville, TN on the Tennessee/Kentucky Border. Strong storms are working through Tennessee and Kentucky, and there is even a Tornado Warning up just West of Nashville. Other thunderstorms are moving through the Northern parts of Mississippi and Alabama. The Storm Prediction Center is considering issuing a Severe Thunderstorm Watch for part of Arkansas and has just issued a Severe Thunderstorm Watch for parts of North Alabama and Mississippi, extending Northward through Tennessee into Southern Kentucky.
THIS MORNING: We are seeing lots of moisture being pumped in from the South, and that, coupled with a very unstable atmosphere is getting some scattered showers and thunderstorms started early across the Twin States. A cold front associated with the Low is draped from roughly Nashville, back to Memphis, through Southern Arkansas, Northern Louisiana, and back into East Texas. That cold front will be the focus for strong to severe storms to fire up later this morning, and move in here this afternoon through tonight.
WHAT TO EXPECT: I anticipate some scattered showers and thunderstorms this morning, with the heavier storms coming in later today. A generous window of severe weather opportunity looks to exist between 12:00 PM through Midnight. I will detail the risks for each mode of severe weather (tornadoes, wind, and hail) below.
TORNADO RISK: The tornado risk is low, but not zero. The atmosphere is extremely unstable this morning, with over 700 J/kg of CAPE (Convective Available Potential Energy) at the surface, and close to 1400 J/kg aloft. Two things are working against surface based storms (which are the ones that produce tornadoes). 1: the best forcing, and turning of winds with height through the atmosphere is closer to the center of the Low. 2: There is a cap just above the surface (an area of warmer air aloft) that will need to be broken. That being said, we may "bust the cap", and there is enough shear to drop a tornado or two today, so we'll have to keep an eye on that.
WIND RISK: Most of our thunderstorms today will be elevated, and most of the instability as mentioned above will exist in the middle part of the atmosphere. Most models indicate that CAPE values could exceed 2000 J/kg this afternoon. If we do bust the cap, then some of the faster winds aloft will be able to mix down to the surface.
HAIL RISK: This is the biggest risk with the storms today. As shown by data from the 7:00 AM weather balloon launch in Jackson, MS, the atmosphere is cooling down extremely fast with height. That means the level at which water freezes is lower, and the strongest storms will be capable of up to golf ball sized hail.
BOTTOM LINE: As the cold front comes through later today, expect strong to severe thunderstorms possible all over the viewing area, with the main risks being hail and gusty winds. There is however a non-zero tornado risk, so there is a possibility of a few tornadoes as well. Make sure you have a way to get warnings, that being a NOAA Weather Radio or a smartphone app. Do NOT rely on outdoor warning sirens to get weather information. We will be updating the web and cutting into TV as needed when the storms approach. Again, the window of opportunity looks to be from 12:00 PM to 12:00 AM, with most of the action occurring around dinner time through about 9:00. Of course, any of this could change, so make sure to stay with us!