A split in the jet stream—common this time of the year during La Niña— has produced the atmospheric conditions ripe for severe weather development in the Ohio River Valley. Shown in this image are the wind speeds at about 3.5 miles high in the mid-atmosphere (500 millibar height) for November 14, 2011. The fast atmospheric winds characteristic of the jet stream can be seen splitting in the Pacific Northwest, with one branch bringing cool air into the U.S. from Canada, while another branch sweeps low into the Pacific and Gulf of Mexico, bringing with it warm, moist air. The union of these two air masses creates the instability associated with severe weather. NOAA is monitoring the situation as high winds, hail, and even tornadoes may possibly result from this weather system. Note that the wind speeds shown here high in the atmosphere are much greater than those to be expected on the ground for most areas.
The second image was taken at 2 pm Eastern by the GOES-13 satellite. The atmospheric instability can also be seen in the disarray of cloud structures – especially the wispy high cirrus clouds. The banding patterns seen in these clouds are also associated with areas of turbulence. In addition, the high over-shooting cloud tops that are characteristic of severe convective weather can be seen forming over central Indiana.