In Western Wisconsin we were on the cold side of a very vigorous and spring-like storm system that marched across the middle portions of the United States. We got a potpourri of precipitation from rain to snow and literally everything in between.
However, down south was a whole different story. Last night into early this morning the same low pressure system that brought us our most significant snowfall this winter also touched down several tornadoes in 9 separate states. 21 tornadoes were reported in all. The strongest of which hit Harrisburg, Illinois at the very early hour of 5:37am. Nighttime tornadoes are relatively rare and the most dangerous and that held very true this time around. Six people died in the town of Harrisburg. Nine people lost their lives in all from the twisters in the region. 100 people were injured in Harrisburg, and close to 200 homes were destroyed in the town that was hit hard by the EF-4 tornado. Below is a picture of the devastation from Paul Newton/The Southern via AP.
Just after 9pm that night, back in the small town of Harveyville, Kansas another twister did the damage in the picture below from John Hanna/AP. Of the small town 40-60% of the structures were destroyed. Several people were injured, one critically.
An EF-2 tornado struck the tourist hot spot of Branson, MO. Meanwhile, Tuesday evening saw a couple tornadoes in Nebraska that not too long ago was hit by a big snow storm. Check out this picture. It's a tornado tearing across the landscape of Nebraska on Tuesday, and if you look closely, you can still see some snow on the ground...crazy! The photo is from Meteorologist Dean Wysocki.
A few of my friends from Iowa State University were tornado chasing in Nebraska yesterday. Here is some incredible video they captured near Elba, Nebraska of a funnel cloud. Thanks to Bryce Link, Ethan Milius, Chris MacIntosh, Tristan Morath, and Tim Marquis for the video!
So how did this system cause all this severe weather? There are several reasons. One of the big factors was the temperature contrast created by the storm. The low pressure system pulled up very warm, moist air from the Gulf of Mexico for this time of year. That's why we saw such heavy, wet snow here in the Chippewa Valley, but for down south it was perfect conditions for severe weather. On the surface map below, the red represents the region that saw all the severe weather. Notice all the severe weather occurred where the warm, moist air and the colder and dry air meet. Another big factor was in the upper levels of the atmosphere. Very strong winds aloft from a very strong jet stream over the area. Also, the winds were changing direction as you go upwards. That kind of shear is key in tornadic development.
Those ingredients coming together just right resulted in a scary night for many folks in the mid-Mississippi Valley as you can see by all the severe weather reports from yesterday into early this morning.
Unfortunately, this system isn't done yet. Tornadoes have already been reported earlier today in Kentucky. The severe weather this evening shifts along the southern Appalachian mountains. From the winter weather to the severe weather to our south, this storm system will be one to remember in 2012.