Convective Instability increasing as seen on Layered LAP PW data

The image below shows a well-defined dry layer advancing east from the lower Missouri Valley into the Mid-Mississippi Valley.  In particular, the 700-300 hPa precipitable water image (upper right panel) shows very dry air working east over low-level air that is characterized by higher moisture.  This signals an increase in convective instability across the Illinois and Mid-Mississippi River Valleys.