Jumping with a shadow in isometric?

So I have a 3D environment with sprites, and I want to have shadow cast on the block below, with the transparency fading at the highest point and then fading back into 100% opacity on the ground below the sprite. The necessity for this, is an indicator of the location of the sprite in space for which block it is positioned over.

Can someone explain pseudocode to do this or know of a resource that teaches how to implement it? It's technically a 2D game but in 3D space. (2.5D?)