Storms lacking, at least for now

The 'Ring of Fire' has set up...and no I'm not talking about Johnny Cash!  A big ridge of high pressure has found a home across the southern states today and will keep any storm activity this afternoon to the north.  Typically when you get these heat domes that set up you'll find storms that ride along the outer edges of them; like for today thunderstorm activity will be found along the northern tier of the U.S.  This is usually where the cap is weaker and it's easier for thunderstorms to form.  The reason for the lack of storms here is because not only do we have warm temperatures at the surface but they're also found above.  In order to get thunderstorms to develop you need rising air.  When you have warmer temperatures above, the air can't rise because the air at the surface isn't less dense than the air above (remember that warm air is less dense than cold air).  As long as the air that is rising is warmer and less dense than the surrounding air it will continue to rise.  The warm air above is what we often refer to as a 'cap' or 'lid' on the atmosphere.  So while the instability was very high yesterday and will likely be high today, we simply won't be able to break our cap.

That will also be the case into early Wednesday.  A strong cold front will come through late on Wednesday and will provide enough lift with it to help break our cap.  This in turn will allow the air to rise leading to storm development.  Because we will have had several days of heat and humidity built up some of the storms could be on the stronger side with gusty winds and heavy rainfall.  By the time the front reaches northern Illinois it will be later in the day so we will have lost some of our instability but may have enough of it to support the storms through the overnight.  Behind this front, a cooler more comfortable air mass will be found that will continue through this weekend.