Breaking down the odds of seeing a tornado

Posted at 8:35 AM, Apr 25, 2016
and last updated 2016-04-25 20:42:34-04

When you hear the 7 First Alert Weather Team (The Most Accurate in WNY) talk about the threat of severe weather heading toward your backyard, what exactly do we mean when we reference "% Chance of T-Storms or Tornados"?

It all starts with the Storm Prediction Center, a part of the National Weather Service located out in Norman, Oklahoma. This is where official warnings for severe weather are generated.

Graphically, the there are five levels of risk.

The lighter shade of green means your area might experience garden variety thunderstorms, but very little threat of severe weather.

The highest level is colored in magenta. If you're in this shade, know that a severe weather outbreak is expected and the possibility of long lasting tornadoes and or a derecho is high. For more information, click here.

The probability maps are not just for T-Storms but also include other types of severe weather like hail, wind and tornadoes. According to their website, "probability values represent the chance of severe weather occurring within 25 miles of any point, which is about the size of a major metropolitan area." OK, I know that's hard to process so try it this way...

For example, the SPC is giving a 2% chance of a tornado in Chicago on Monday.  This means that if you live in Chicago or in the surrounding suburbs, the odds of seeing a tornado in 25 miles of where you are located is 2%. Now wasn't that easier?

These maps are generated for wind, hail and tornadoes on the day when severe weather is expected. Day two and three outlooks will lump all three severe weather elements together like you see below.

While a few rumbles of thunder in our neck of the woods over the next couple of days is not of the question, parts of the Midwest and South Central U.S. will be bracing for a major severe weather outbreak on Tuesday.

Ingredients for a severe weather outbreak include moisture, difference in wind speed, plenty of lift and a trigger mechanism.

In this case, plenty of moisture, a mid level disturbance along with a strong mid level jet and a dry line will help spark deadly tornadoes, large hail and damaging winds across a wide swath of the U.S. affecting millions of people grabbing the attention of every major news network for the next couple of days.