How did the sleet weather come from?

At the end of autumn and the beginning of winter, the weather in Jianghuai area of China is cold, and rain and snow often come together for a relatively long time, so there is a weather proverb of "sleet, no stop" circulating in this area. Why do the above weather phenomena occur in Jianghuai area?

Jianghuai area in China is the channel where the cold air in the north goes south and the warm and humid air in the south goes north. After autumn, the cold air in the north is dominant, and the probability of cold air going south increases. Cold air going south often causes rainy weather. In winter, the influence of cold air is stronger. At this time, the temperature in the Jianghuai area is also relatively low. Once there is strong cold air going south, the ground temperature often drops below 0℃, which makes the excess water vapor in the air condense into small ice crystals. When many small ice crystals increase, they become big snowflakes. So it usually snows in winter in Jianghuai area.

Sometimes the warm and humid air flow in the south is strong, which will slow down the speed of cold air going south. When cold and warm air meet and form a front in Jianghuai area, warm and wet air will climb to the front and cool and condense into a large cloud area. If the near-surface temperature is above 0℃, the small ice crystals falling from the clouds may all melt into rain, and the large ones will partially melt into wet snow. So when landing near the ground, there is both snow and rain, which is called sleet.

Due to the strong influence of warm and humid air, the front between cold and warm air can stay in Jianghuai area for a long time, and the warm and humid air keeps climbing on the front, cooling and condensing, thus forming a wide range of sleet, and the weather will not clear up soon in a short time. So "sleet, nonstop" is the most common weather in Jianghuai area of China.