What weather system is the main influence of winter precipitation in southwest China?

Winter precipitation in southwest China is mainly affected by Kunming quasi-static front.

As shown in the figure, cold air from the north meets warm air from the south in winter to form a cold front, which moves south (center plane A in the figure) and is blocked by Yunnan-Guizhou Plateau, so the moving speed of the front slows down and turns into a quasi-static front.

The A front in the picture below is a quasi-static front in Kunming, Yunnan-Guizhou Plateau. About 104 E line as the boundary, the meteorological conditions on the east and west sides are obviously different. Guiyang is located on the warm air side in front of the quasi-static front, and it is sunny and warm in winter. Kunming is located on the cold air side behind the quasi-static front, which is rainy in winter and has little sunshine.