For severe weather to happen, there are four ingredients we usually look for: Instability, shear, moisture, and lift. Instability can come from a difference in air temperatures, and oftentimes, instability can come from daytime heating by the sun. Lift also comes from differing air temperatures. Wind shear is the difference in speed or direction of wind in a certain area. Moisture is any presence of water in the atmosphere.
In Thursday's case, moisture is being brought to mid-Missouri by southerly winds. These winds are dragging air from the Gulf of Mexico northward, and that moist air helps with our storm chances.
The differing air temperatures are also being aided by these southerly winds. In addition to that warmer wind, the incoming system that is going to be setting up these storm chances has a warm front ahead of it. This warmer air will combine to create an unstable atmosphere that allows for those storms to develop.
Lift is often caused when two air masses, one cool and one warm, stack upon each other. In this case, a cold front will be moving through the area and clashing with that warm, moist air that is already in place. This will force the air on top of each other and create upward motion or lift.
Finally, wind shear for Thursday will be coming from the combination of the low pressure system and southerly winds. As the system pushes in from the northwest, it will collide with southerly winds. The stronger of the two will force the other off to the side. These changes in wind direction can help spin up tornadoes, which is a concern we have with Thursday's system.
Lacking just one of these factors would greatly reduce our severe weather chances, but latest guidance is suggesting that all of these factors will be in play. If you want to know more about what to expect Thursday, check out our Insider Blog on the incoming system.