Cold, dry air sweeping down from Canada mixing with warm, moist air from the Gulf of Mexico and Pacific Ocean are merging in the U.S. Plains today, creating conditions for some very turbulent weather. A tornado outbreak today in the early morning hours caused destruction in Kansas and Oklahoma. This image shows the air temperature at 40,000 Pascals (about 23,000 feet high in the atmosphere) using data outputs from the NOAA North America Model for 2100z on May 20, 2013, combined with an overlay of the winds at the same elevation. Tornadoes typically occur at the convergence of these two different air masses. A distinct boundary of "cold meeting warm" is visible in this temperature data, extending from Texas into Illinois.