DENVER (CBS4) – A weather system moving out of Utah will help spark some strong thunderstorms across Colorado during the afternoon and evening hours on Friday. There is even potential for a few to reach severe criteria with wind gusts of 58 mph or greater. For a storm to be considered ‘severe’ one or more of the following must be observed…
For a thunderstorm to develop you need rising air that is warm and humid. We are very warm today for late April and we have a rising motion in the atmosphere thanks to daytime heating, the interaction of wind with terrain, and a weather disturbance moving out of Utah. But we are lacking the ‘humid’ part of the necessary ingredients.
This is where we turn to the dew point, which is a measure of how much moisture is in the air. (and this matters because moisture holds latent heat, or potential energy to help fuel storms) Most places on the planet look for a dew point in the mid 50s or higher to spark thunderstorms, but a high altitude environment like Colorado can experience thunderstorms with dew point temperatures as low as 35 to 45 degrees. (preferably 45 or higher)
As of 1 p.m. Friday most dew point temperatures across Colorado were less than 40 degrees which indicates dry air near the surface. This is important to note because that means there will be a lot of evaporation associated with any thunderstorms that develop Friday afternoon, and the amount of ‘fuel’ to feed storms is limited.
When rain falls out of a thunderstorm and into dry air below the evaporation creates pockets of cooler air that sink because cooler air is more dense than warm air. On the ground the result is the potential for strong, gusty winds that can reach speeds of 58 mph or greater, making them severe and potentially causing damage.
For a person caught in one of these storms it can be odd to experience a severe thunderstorm that has little to no rain or hail, but a lot of high wind.