My Crappy MSPaint Take on the Rain vs. Snow Issue

 

It's archaic, but this somewhat describes why we sometimes see all snow, a mix, or all rain. It highly depends on the temp about 100-1000 feet above the ground.

The higher up the 32 degree line is and larger span it crosses, the more ice and rain we see. The closer the 32* (or lower) line is to the surface, the more snow we see.