As solar radiation begins heating the Earth's surface each morning, the daily convective cycle begins. In other words, air nearest to the surface begins heating, rising, cooling, falling, and so on. This motion "mixes" the PBL, allowing for air parcels to come closer and closer to their LCL.
After air parcels reach their LCL, they will, at some level nearby, begin rising without the aid of their lifting mechanism (fronts, thermals, mountains or "orographic" lifting).
As parcels freely convect, their condensed (liquid) water droplets begin to aggregate or "clump" together, creating larger droplets. This process is generally accelerated by condensation nuclei....