Abstract: To improve the forecasting capability for short-duration heavy rainfall processes in Ganzi Prefecture of the Western Sichuan Plateau on the eastern Tibetan Plateau, this study uses hourly precipitation observation data from 18 benchmark (basic) meteorological stations and 489 regional meteorological stations in Ganzi Prefecture. Datasets cover the flood season (April–October) of 2012—2021, alongside conventional MICAPS upper-air soundings from the China Meteorological Administration (CMA) and hourly ERA5 reanalysis data at a horizontal resolution of 0.25° × 0.25°. This study investigates the synoptic classification, circulation characteristics, conceptual models, and physical environmental parameters of short-duration heavy rainfall during the flood season in Ganzi Prefecture, Western Sichuan Plateau. The results show that: (1) The trough-tail shear type and plateau shear line type are the dominant synoptic patterns for short-duration heavy rainfall in Ganzi Prefecture. The upper levels of both types are influenced by the South Asian High, and the mid-level T-Td is less than 3℃. For the trough-tail shear type, the tail shear line of the Lake Baikal low trough or the northeast low trough affects central Ganzi Prefecture, and the Western Pacific Subtropical High is located near 110°E. In contrast, the shear line type is mainly affected by the oscillatory plateau shear line, and the Western Pacific Subtropical High is located near 105°E. (2) Under favorable synoptic-scale circulation, physical environmental parameters corresponding to local short-duration heavy rainfall present distinct characteristics. For both types, the 500 hPa T-Td at Ganzi station is below 2°C, the 500 hPa wind at Wenjiang station is southwesterly, and the 700 hPa wind at Xichang station is southerly with specific humidity exceeding 12 g/kg. At 500 hPa, Ganzi Station features northerly winds for the trough-tail shear type and northwesterly winds for the shear line type. At 850 hPa, Wenjiang Station exhibits northeasterly winds with specific humidity exceeding 15 g/kg for the trough-tail shear type, while for the shear line type, the station has northeasterly or southeasterly winds with specific humidity exceeding 16 g/kg. (3) The establishment of low-level water vapor transport channels and water vapor convergence are conducive to the generation of short-duration heavy rainfall in Ganzi Prefecture. Both types are accompanied by positive relative vorticity and vertical upward motion in the mid-to-lower troposphere, as well as a large vertical gradient of pseudo-equivalent potential temperature. Compared with the shear line type, the trough-tail shear type has weaker upward motion but sufficient water vapor supply, and the low-level easterly winds over Ya'an are clearly orthogonal to the local terrain, triggering obvious terrain-forced lifting.