Snow plus warmish day equals fog: advection fog

It snowed the other day. The ground was still deep in snow early this morning. But come mid-day, a warm breeze from the south began melting the snow and soon thick fog covered the ground.

This is called Advection Fog: It forms when a warm, moist wind from the south encounters snow covered ground. This contact between warm air and cold, moist ground causes the air to become cool, saturated with moisture and fog is formed.