Severe thunderstorms are a common weather hazard in Northwest Arkansas and the River Valley, but what are they? A severe thunderstorm is defined as having at least one of the following criteria:

• Wind gusts of 58 mph or greater
• Quarter-size hail or larger (1-inch or more in diameter)
• Tornado

In anticipating of these storms, the National Weather Service (NWS) may issue a severe thunderstorm watch.

Severe Thunderstorm Watch

A severe thunderstorm watch will be issued for an area when ingredients are beginning to come together that could lead to severe thunderstorm development.

Issued by the Storm Prediction Center (SPC), severe thunderstorm watches can cover widespread areas (sometimes multiple states at once). They can last for several hours as the severe weather pushes through the region.

What does this mean for you and your family? Watch the sky and monitor the weather.

A severe thunderstorm watch does not mean severe storms are necessarily occurring at that moment. If a severe thunderstorm warning is issued, that is when you need to take action.

Severe Thunderstorm Warning (Traditional)

Severe thunderstorm warnings may be issued by your local NWS forecast office if at least one of the aforementioned requirements for severe thunderstorms is met. They are smaller than watches in coverage size and are generally short-lived (generally an hour or less). If a warning is issued, then severe thunderstorm conditions are imminent or occurring and you need to take action.

If you are outside, head into a building (especially if you can see lightning or hear thunder) and remain away from windows. Severe thunderstorms can produce wind gusts that cause damage to windows and break them. While you may think it’s unlikely this will happen to you, it’s always better to be safe than sorry in the end.

True or false – you can only get severe t-storm warnings if a watch was issued ahead of time.

FALSE. While more widespread severe thunderstorm events generally have a watch ahead of time, there is no requirement that a severe thunderstorm watch needs to be issued before a severe thunderstorm warning. We’ve had numerous examples of this in Northwest Arkansas and the River Valley. Sometimes thunderstorms just get an extra “kick” and develop stronger than the models suggested.

This is why it is important to ALWAYS pay attention to the weather, especially if you are going to be outdoors. Keep in mind a thunderstorm does not need to be severe to be dangerous.

Severe Thunderstorm Warning (Tornado Possible Tag)

Remember those three ways you can get a severe thunderstorm warning? One of the ways is to have a thunderstorm produce a tornado.

If a severe thunderstorm is capable of producing a tornado, the NWS may issued a “tornado possible tag” within the severe thunderstorm warning.

Why not just issue a tornado warning? There are a few reasons for this.

• First, a severe thunderstorm may not be producing a tornado at that time, but the environment is very favorable for the rapid development of one. Instead of issuing tornado warnings and making everyone take cover when there is nothing happening yet, the NWS will issue this tag to warn the public of the potential danger down the road.
• Second, a severe thunderstorm may appear to be in the beginning stages of tornado development on the radar. However, some of these signs can also point to other things, such as straight-line damaging winds. Using the tag warns the public without triggering a tornado warning and increasing the number of false alarms an area experiences.

If this tag is issued by the NWS service and you’re watching your NWA Weather Authority team, a dark orange outline will appear around the severe thunderstorm warning (example below). In a traditional warning without this tag, this outline will be the lighter orange you see filling in the polygon.

Regardless if a thunderstorm is severe or not, they are all potentially dangerous. All thunderstorms produce lightning by definition (you can’t have thunder without lightning). This is why you always want to go inside during a thunderstorm. As the saying goes – “When Thunder Roars, Go Indoors“.

Send Us Your Questions!

Have a weather question for your NWA Weather Authority team? Email us at weather@knwa.com!