A major tornado outbreak is on tap for parts of the southern and midwestern United States this afternoon, with a high likelihood for large, violent, long-track tornadoes extending from Louisiana north through Nebraska.
The above map is the tornado probability forecast from the Storm Prediction Center issued at 11:30 this morning. The percentages refer to the probability of seeing at least one tornado within 25 miles of any point within the shaded area. A 5% risk for tornadoes is concerning, so 10-15% are relatively high. The black hatching refers to the chance for large, violent, long-lived tornadoes.
This is the kind of tornado outbreak where we see classic supercells with the hook echo and debris balls, and the chance for wedge tornadoes that tear up miles upon miles of land. The majority of the thunderstorms might be a little more "subtle" on radar, producing large tornadoes but not giving the 'classic' appearance. This makes it more dangerous, especially since A) the tornadoes could be rain-wrapped, and B) people who don't know what they're doing might glance at the radar and think they're fine.
The SPC still mentions that they may have to raise the chance for severe weather -- including tornadoes -- to a "high risk" (5/5 on the severe weather scale) in subsequent outlooks.
Please go to the Storm Prediction Center's website for the latest forecasts, and spread the word that strong tornadoes are possible today.
As usual, I will publish and update severe weather liveblogs as conditions warrant this afternoon. Fair warning: those diaries are image-heavy, with lots of radar images, screenshots of live news feeds, and other pictures of tornadoes/damage as they happen.
I write for The Vane, which is a new weather website I launched with Gawker. You can also follow me on Facebook and Twitter.
10:45AM CDT: Good morning. Severe thunderstorm watches are in place from Texas to Kansas for a broken line of thunderstorms moving east, mostly producing hail and damaging winds. It should be interesting to see what happens as these storms move into the risk zone over the area stretching from Nebraska to Louisiana. The storms today will be a mixture of these existing storms as well as new storms that pop up aided by daytime heating. The big batch of rain and storms over the Mississippi Valley (center of the pic) left a large area of stable air over Arkansas, but it should start to mix out as the heat of the day builds. The atmosphere is still capable of producing violent, long-track tornadoes later today everywhere in the risk area outlined by the SPC in the map at the top of this diary.
11:37AM CDT: The latest outlook from the SPC is out and I've updated the map accordingly. They've reduced the area at risk for a major tornado outbreak, and they're still using strong language: "significant severe weather episode [...] a few strong, long-track tornadoes possible."