The driving force behind Sunday's severe weather

Historic storm buries Upper Midwest in feet of snow

By Jonathan Kegges - Meteorologist

ROANOKE, Va. - It's been a rough couple of days for those affected by Sunday's storms. An unseasonably warm and moist air mass in place set the stage for the widespread damage observed by many across southwest and central Virginia.

To get severe thunderstorms and tornadoes, you need all the ingredients to come together. If you're missing the eggs while making a cake, it's not going to taste right. The same holds true for a severe weather set-up. On Sunday April, 15 those ingredients came together.

Temperatures surged into the mid-70s with dew points in the low to mid-60s. The higher the dew point, the more moisture is present in the atmosphere.  Dew points, like they ones we had Sunday, are high enough to fuel thunderstorms.

Picture the above ingredients as being the fuel. To get that fuel to ignite, you need a match. A very strong upper level low over the Upper Midwest was the trigger to get it all started. It not only drove colder air south to initiate thunderstorms, but also provided this part of the country with directional wind shear, changing of the wind direction with height, for thunderstorms to rotate. The green circle on the map below represents where we live. The brighter colors represent very strong winds at about 15,000 feet off the ground. 

The strongest storms pushed through late Sunday afternoon through the evening. 

Below are shear tracks, basically the radar picking up on the rotating thunderstorm. There likely wasn't a tornado associated with the rotation the whole time, but where the colors show up indicates that rotation was present in the storm.

An EF-1 Tornado was confirmed in Craig county and a strong EF-2 tornado was confirmed in Campbell/Amherst counties. The National Weather Service was still assessing the strength of a likely tornado in Pittsylvania county as of 11 a.m. Tuesday morning. 

Leading up to and during our severe weather locally, the Upper Midwest was being crippled by the same storm with feet of snow and blinding winds. Below is a map from the National Weather Service of the measured snowfall totals from April 13 to 15.

We are just in the beginning of severe weather season. Now would be a good time for you and your family to practice your action plan should severe weather strike.

 

 

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