What is an MCS?

M.C.S. ... A common summertime storm phenomenon but what is it? 

A mesoscale convective system, or m-c-s for short, is an organized complex of storms that typically lasts for several hours or more and spans across multiple states. In the summertime, MCS’s usually happen at night as individual thunderstorms from the daytime hours organize into complexes. Most commonly, MCS's are linear, like squall lines. The primary threats during MCS’s are usually strong winds and heavy rainfall but they can contain damaging hail and tornadoes too. 

Some MCS’s are MMC's or mesoscale convective complexes which are large, circular long-lived clusters of showers and thunderstorms. Another less common type of MCS is a mesoscale convective vortex - which almost resembles a small hurricane - or a derecho, a particularly destructive wind-driven MCS. It is always important to know your risk, and to have multiple ways to receive alerts about these types of storm systems.