Weather Word of the Week: MCS

Weather Word of the Week

Weather Word of the Week: MCS

Welcome to Weather Word of the Week! I am excited to continue your education in the fascinating world of weather. Each week I will introduce a weather-related topic that will impact our forecast for that week. We’re kicking off this new digital segment with the phrase MCS!

Infrared Satellite Image of a MCS Over the TX Panhandle 06-20-20

This weather acronym stands for Mesoscale Convective System. Simply put an MCS is system of thunderstorms that stretches over 60 miles in any particular direction. These storm systems can take the form of a line, a cluster, or even a bowing segment. MCS’s can also move very fast often driven by the strong damaging winds that gust out ahead of them.

Our geographic location sets us up in a prime location to see impacts from these storm systems. During the summer we are often positioned on the east side of a high pressure. The winds with high pressure circulate clockwise, so that means we see northwest winds aloft. Storm complexes that form in the northern great plains overnight will often ride the upper level winds moving SE into our region.

Once these storms arrive, they can bring a variety of impacts to Northwest Arkansas and the River Valley. The top three impacts come from flooding, damaging wind, and lightning.


The large size of these thunderstorm complexes can lead to flash flooding quickly if they stall out over a region. Sometimes a MCS will move parallel with the upper level winds, and this causes the storm systems to slow down quite a bit.

A regular thunderstorm can dump a tremendous amount of rainfall if it is slow moving. Imagine if a storm system of thunderstorms over 60 miles wide stalled out over a region! It would produce massive rainfall amounts over the same locations. This can lead very quickly to flash flooding scenarios. Remember that if you see water rushing across a road to “Turn Around, Don’t Drown!” It only takes 6 inches of moving water for you to lose control of your vehicle and 2 feet to sweep it and you away!

Flash Flooding Caused by a MCS in Kansas

Damaging Wind

As mentioned earlier, MCS’s are driven by strong often damaging winds. No surprise that these strong winds can cause damage along the leading edge of these systems.

These damaging straight line winds are formed within the downdrafts of the storms and are often aided by strong low level winds just above the surface. The low level winds get sucked into the backside of the storm complex and are driven to the ground enhancing the power of the winds surging out ahead of these powerful storms!

The gusty winds can reach speeds of over 80 mph! They can topple trees and also cause severe structural damage to some buildings.

Structural Damage Caused by a MCS


A dangerous impact that might not make headlines often is lightning. These storm systems can produce a lot of this electricity! A MCS can produce over 31,000 strikes in about 6 hours!

There is a good reason why the National Weather Service stresses that “When Thunder Roars, Go Indoors!” Lightning can strike up to 10 miles away from the parent thunderstorm. This means you could be in danger and not even be aware of it!

Our NWA Weather Authority App is free to download on your favorite device, and it can alert you when lightning and rain is nearby! You can download our app on iTunes: or Android:

Once safely inside, you can sit back and enjoy the natural firework show. Some of my favorite summer memories growing up was sitting out in our screened in porch and watching the vivid lightning from these storms as they approached!

MCS Lightning Show

I hope you enjoyed learning about what an MCS is during this segment of Weather Word of the Week! Look for more content on our website. Have a great rest of the week and stay healthy!

Copyright 2020 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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