Twin Falls, Idaho (KMVT/KSVT) Friday night over Hansen, Murtaugh and Kimberly many people reported to the KMVT Local 11 Weather Center seeing a funnel clouds. What you saw was not the beginning of a tornado but what is classified as a cold air funnel. It was nearly two years ago today (May 19, 2015) the last time we saw cold air funnels in Southern Idaho.
These funnel clouds, although associated with a passing thunderstorm around 6:45 p.m. Friday night, are different than the funnels and tornadoes you are familiar with.
Idaho is not immune from tornadoes, the weather conditions and environment Friday night were very different than the conditions that form the strong destructive tornadoes most people associated with funnel clouds.
First you need to understand the difference between a funnel cloud and a tornado. A funnel cloud is rotation coming down out of a cloud but NEVER reaches the ground. Once a funnel cloud or the rotation reaches the ground, then it is classified as a tornado.
The cold air funnels we saw Friday was associated with cold upper low pressure systems that brought the rain to Southern Idaho and cool temperatures Friday. These funnels are usually weak and rarely touch the ground. When they do touch down, the resulting tornadoes are small and relatively weak causing little to no damage.
On the other hand, the funnel clouds that produce the tornadoes most people are familiar with come from severe thunderstorms. Many of these severe thunderstorms are supercell storms that are rotating and spinning themselves. Unlike cold air funnels that form in a relatively cool and cold atmosphere, tornadoes associated with severe storms form in a very warm moisture rich atmosphere that helps give the storm its strength and fuel.
Idaho can and has seen strong damaging tornadoes before. The state averages somewhere around 6 tornadoes a year. Most occur in the eastern part of the state but we can see tornadoes here in the Magic Valley and the Wood River Valley. Most tornadoes that form in Southern Idaho are between an EF-0 and an EF-1. There have been a few EF-2, but they don’t happen very often.