The macro- and microphysical characteristics of wintertime precipitating clouds and non-precipitating clouds over the West Tianshan Mountains, China, were analyzed with the use of Ka-band radar and weighing rain gauge observations. The data were collected from January to February 2019, December 2019, and from December 2020 to February 2021. Snowfall clouds mainly ranged from 0.15 ~ 2.50 km and had a reflectivity (Z) of mostly 10 ~ 33 dBZ. Non-snowfall clouds were primarily distributed within the height range of 2 ~ 8 km, and the Z values were within the range of − 22 ~ 15 dBZ. Compared with non-snowfall clouds, snowfall clouds have a higher particle water content (M) but a similar radial velocity (V). Light and moderate snowfall clouds were mainly located at heights of 0.15 ~ 3.50 km and had Z values concentrated from 5 ~ 24 dBZ. Heavy snowfall clouds were characterized by a Z of 5 ~ 30 dBZ below 3.5 km. The proportion of clouds with an M value > 0.1 g·m⁻³ below 2 km was noticeably higher for heavy snow events than for light and moderate snow events. The differences in the distributions and values of snowfall cloud V values were small among the different snow types, and descending motions occurred below 6 km, with V ranging − 1.4 ~ − 0.3 m·s⁻¹. The heights of the non-snowfall cloud top and base during the day were lower than those at night. The snowfall cloud top did not show noticeable diurnal variations. The cloud top and base heights of the non-snowfall clouds both showed a single-peak distribution. The cloud top values of snowfall clouds exhibited bimodal distributions.

On 31 July 2021, an extreme orographic rainstorm hit northern Hami in central Asia. This study diagnoses the evolution of the low-level jets (LLJs) and accompanying moisture, thermodynamic, and dynamic fields before and during the "7·31" rainstorm to reveal its multi-stage triggering mechanisms. The main findings are as follows: (1) Before precipitation, zonal geopotential gradients sustained a Hexi easterly LLJ transporting moisture and accumulating CAPE over Hami, while cold air piled up north of the Tianshan Mountains to form a deep cold pool. (2) At the precipitation onset, 700 hPa easterly jet deflection steepened the horizontal θse gradient, and terrain lifting triggered initial rainfall. Vertical advection and subgrid residuals jointly boosted local 700 hPa southerlies, whereas Coriolis-horizontal advection and zonal geopotential gradient dominated 650 hPa southeasterly jet intensification. (3) At the peak stage(1900 UTC), 650 hPa southerlies were governed by meridional advection and geopotential gradient, and cross-layer subgrid residual exchange strengthened 700 hPa southerlies. Superimposed warm-cold frontal updrafts and 650–700 hPa moisture convergence synergistically drove rapid rainfall amplification. The layered dynamical distinctions between 650–700 hPa LLJs provide diagnostic references for forecasting arid mountain-basin extreme precipitation in Northwest China.