Why does cold front weather affect thicker clouds?

In the process of moving, the cold air mass plays a leading role, pushing the front surface to move to the side of the warm air mass. Cold front is the abbreviation of cold front, the front of cold air mass heading south, and the most common weather system affecting China, especially in winter. In winter, a cold air invades the inland from northwest and north China every few days. When the cold front crosses the border, it will be accompanied by the increase of northerly wind, the increase of air pressure and the decrease of temperature, sometimes causing rain and snow, and even heavy rain in summer. Under normal circumstances, after the cold front crosses the border, the local area will be subjected to cold high pressure.