Tibetan Plateau (TP) has experienced significant warming-wetting trends in recent years, inducing snowfall changes. However, the relative roles of precipitation and temperature in driving changes in snowfall and subsequent snow-hydrological processes remain poorly understood. We use China Meteorological Forcing Dataset (CMFD) v2.0 to quantify the contribution of meteorological factors including precipitation and air temperature to variations in snowfall. The results indicates that snowfall variability arises from complex interplay of both synergistic and competing effects between warming-wetting trends, with pronounced spatiotemporal and seasonal heterogeneity. Precipitation is the primary factor dominating snowfall variation during different stages, affecting snowfall changes across 66.42 % areas of the TP. The compensatory effect of precipitation change offsetting warming-induced snowfall decline has intensified, especially after 2000, with positive contribution of 15.28 mm. Besides, the contribution mechanisms governing snowfall changes show phased elevation dependence, with mid-to-high elevation regions exhibiting greater sensitivity. Furthermore, sensitivity analyses based on the SSiB3 (Simplified Simple Biosphere Model version 3) land surface model reveal that warming-wetting induces cascading impacts through the “warming-wetting-snowfall-snow cover-snowmelt runoff (SMR)” chain. This cascading process leads to an overall increase of 2.2 % in cumulative SMR, accompanied by enhanced spatial heterogeneity and seasonal variability of snowmelt. Distinct responses are observed among different snowfall-contribution regimes, snow regimes, and elevation bands. Changes in dominant climatic factors reshape the seasonal distribution of SMR. These findings reveal the complex mechanisms linking snowfall changes to cascading snow-hydrological responses under a warming-wetting climate over the TP, providing novel insights for water resource assessment and future climate adaptation.