the first signs of changing weather appear long before the front is actually over you. Initially, the air is cold: the cold air mass is above you and the warm air mass is above it. High cirrus clouds mark the transition from one air mass to the other. Over time, cirrus clouds become thicker and cirrostratus clouds form. As the front approaches, altocumulus and altostratus clouds appear and the sky turns gray. Since it is winter, snowflakes fall. The clouds thicken and nimbostratus clouds form. Snowfall increases. Winds grow stronger as the low pressure 51. approaches/passes. As the front gets closer, the cold air mass is just above you, but the warm air mass is not too far above that. The weather worsens. As the warm air mass approaches, temperatures rise and snow turns to sleet and freezing rain. Warm and cold air mix at the front, leading to the formation of stratus clouds and fog. 52. "Drag and drop" (insert) matching graphic on the SRS. More often than not, these weather fronts are not isolated events. Often times, they are part of a larger rotating system called a mid-latitude cyclone. This type of cyclone is a 53. low pressure system/high pressure system that is usually mixing warmer air from the 54. south/north (in the Northern Hemisphere) and colder air from the 55. north/south. Watch this video on Mid-Latitude Cyclones: https://www.youtube.com/watch?v=MdfeyJdICXc.