Added on: July 12, 2011
It’s the last day of June and you are planning a flight from Des Moines, Iowa southbound to Springfield, Missouri during the mid-afternoon. Temperatures are expected to climb into the upper 90s throughout most of the Midwest. During your preflight briefing in the morning, you notice a huge amount of instability with lifted index values in excess of -10 along your entire route at 2100 UTC. Most pilots have been erroneously taught that a negative lifted index of this magnitude usually results in an outbreak of severe thunderstorms. Despite the high amount of instability, we’ll examine in this workshop why thunderstorms are not likely and why the sky will remain mostly clear along your entire route of flight during the afternoon.