The clouds that come before a cold front are often cirrus clouds, followed by altostratus clouds, and finally nimbostratus clouds.

Here's a breakdown:

* Cirrus Clouds: These are thin, wispy clouds made of ice crystals. They are the first sign of an approaching cold front and often appear high in the sky, resembling horsetails or feathers.

* Altostratus Clouds: These are gray or bluish clouds that cover the entire sky. They are thicker than cirrus clouds and often produce a hazy or milky appearance.

* Nimbostratus Clouds: These are dark, gray, and often rain-producing clouds. They can be very thick and may obscure the sun completely. They are a sign that the cold front is getting closer and precipitation is likely.

Important Note: While the sequence of cirrus, altostratus, and nimbostratus clouds is typical, the exact cloud types and their appearance may vary depending on the strength of the cold front and other atmospheric conditions.