Forecast discussion for severe weather event (8/16/2012)

As Thursday the 16th comes closer, it appears that a decent frontal boundary is going to make its way through the Indiana region bringing about thunderstorms and cooler temperatures. I'm going to provide an in-depth look at the weather that will be moving through Thursday evening and the processes involved. The first thing to take notice of is the timing of the frontal boundary. According to the 850mb temps, cold air advection can be seen through weak solenoids around Michigan, Wisconsin and Northern Illinois on Thursday late afternoon/evening. The represented area is where cold air is moving into and will receive the greatest initial cool downs. Once the trough deepens and pushes southward, cooler temperatures will extend on into Indiana by Friday. Not only will temperatures decrease due to this frontal boundary but thunderstorms will also be heightened. As the front pushes through the area, low level lapse rates will increase giving way to higher surface based CAPE values. After examining NAM model outputs, CAPE should extend well into the 2-3,oooJ/kg range which is conducive to pretty strong thunderstorms. Any novice could look at the map and make a guess as to where the severe weather is going to occur but not so fast. Thunderstorms are much like recipes in that they require multiple ingredients to fire. While CAPE values are good in portions of Southern and North Western Indiana, wind shear is not so good. Helicity is a measure of the cork screw or turning motions through out the atmosphere. Generally, you would want to look at the the first km of the atmosphere to determine whether or not it is conducive for tornadic weather. After examining the 0-1km helicity values, it's apparent that there is very little to no turning in Indiana. In fact, there is very little 0-3km shear which is supportive of MCS or "a line of thunderstorms." Also, stronger jet streaks aloft are prominent in the Illinois region and not Indiana. Jet streaks are crucial for strong storm development because it allows for the storms to grow in strength. In conclusion, Indiana will receive light to moderate multi cell thunderstorms that could be capable of strong winds. I would say that there is a small possibility of hail/severe type weather but no chance for tornadoes. After storms have moved through, I would expect to see temperatures return to the mid 70's with lows in the 50's making the weekend feel pretty nice.