Based on conventional observation data and ERA5 reanalysis data, this paper analyzed and compared two rare winter snowstorms in western Hunan during December 25-26, 2021 (referred to as process Ⅰ) and February 21-22, 2022 (referred to as process Ⅱ). Results show that both snowstorms occurred and developed under similar weather conditions with stronger-than-normal southwesterly before the southern trough and cold air before mid-high latitude pressure ridge; however, stronger cold air dominates process Ⅰ, while process Ⅱ is controlled by stronger low-level southwesterly with a shear line and thus persistent water vapor convergence. Process Ⅰ shows a noticeable transition from a cold-warm-cold inversion layer to a cold inversion layer with air temperature entirely below 0 ℃, mainly with pure snow; in contrast, process Ⅱ already exhibits an inversion layer that favors snowfall from the beginning, but the precipitation type varies previously and only convert to pure snow later. In process Ⅰ the southward cold air acts to force warm and wet southwesterly uplifting with strong frontogenesis, whereas in process Ⅱ the warm and wet southwesterly climbs along surface quasi-stationary front with relatively weaker frontogenesis. Meanwhile, there exists local secondary circulation accompanied by positive vorticity in both processes. These provide favorable conditions of dynamical uplifting. In addition, heavy snowfall areas in both processes matches well with low-level meso-scale conditional symmetric instability, especially for process Ⅱ during which the conditional symmetric instability is closely related to the downward propagation of upper-level moist potential vorticity.