Wow, it’s cold outside for this time of year. Temperature check at Trussville around 1245 pm, during one of the showers, showed 43 degrees. If we actually stay below 50 degrees all afternoon, it would make it only the 4th time that’s happened in the month of April since 1970. Even if we stay below 55, this will be the latest in the year that has happened since April 19, 1983.
With the very cold air coming in just off the surface, but the warm ground and strong April sunshine trying to warm things up right at the ground, the air at low-levels is very unstable. Check out the temperature profile from the UAH Microwave profiling radiometer around 1 pm.
Temperatures at the ground are near 50, but at an altitude of 1000 feet it was 37 degrees. Temperatures are near 20 at 4,000 feet. At low-levels, the change in temperature with height is about 13 degrees per 1,000 feet, more than twice the equilibrium line for stability vs. instability, and more than we see on some Summer days. Because of this, the air is very unstable, so parcels of air are going up and down very quickly in convective cells, producing small areas of clouds and precipitation, surrounded by small areas of sunshine. Check out the cells on the latest visible satellite picture and BMX radar image.
With the temperatures being so cold at low-levels, some of the precipitation is reaching the ground as sleet in many areas. Just got a report of moderate sleet hitting the windows at Sid Coleman’s office in Tarrant. Neat stuff.
