When warm and cold air collide, warm air is pushed up and can form clouds.
What Clouds Are Associated With a Cold Front?
Weather Fronts and Surface Maps
Fronts CK-12 Foundation
Image Gallery Center for Science Education
CLOUD DEVELOPMENT
Image Gallery Center for Science Education
Lesson 4 Meteorology, PDF, Cloud
Geography 101 Online
Occluded Front: when a cold front overtakes a warm front
Lesson 4 Meteorology, PDF, Cloud
CLOUD DEVELOPMENT
Weather Fronts Explained (Cold, Warm, Stationary, Occluded