Formation of lumps of mid-level clouds with isolated showers not reaching the ground due to an underlying layer of very dry air causing precipitation to evaporate before reaching the surface. In fact the weather sounding (first thumbnail) shows the ideal situation. Clouds had formed due to an infiltration of moist air at mid-levels despite the presence of a high pressure system. Note that as seen from satellite these clouds formed on the Western side due to a shortwave and then broke quickly upon moving deeper into the high pressure.