Snowstorms frequently occur in spring over the heterogeneous underlying surface of the Tibetan Plateau, causing both economic and societal damage. What the intensity of factors triggering snowstorms remains poorly understood. This study quantitatively diagnoses water vapor, the thermodynamic and dynamic conditions of a large-scale heavy snowfall event over the Tibetan Plateau using reanalysis data. Here we show, a cold vortex, the Southern Branch Trough and a meridional shear line are favorable synoptic systems. The snowfall is characterized by low-layer (− 8.3 × 10⁻⁷ g s⁻¹ hPa⁻¹ cm⁻²) and whole-layer (− 4.5 × 10⁻⁴ g s⁻¹ cm⁻²) moisture convergence, low-level atmospheric convergence and high-level divergence (± 3 × 10⁻⁴ s⁻¹), low-level positive vorticity (4.8 × 10⁻⁴ s⁻¹) and strong vertical velocity (− 4 Pa s⁻¹). Although the convectively-stable stratification acted to suppress snowfall, the abundant water vapor and strong orographic uplift of Himalayas and the downhill wind speed convergence overcome this to trigger the heavy snowfall event witnessed in March 2017. These diagnostic results are well consistent with those from WRF simulation. Our study acknowledges the importance of WRF in diagnostic analysis, deepens the understanding of evolution mechanisms and provides theoretical references for accurate forecasting of such events over the Tibetan Plateau. It would aid the development of effective strategies for sustainable livestock, and the mitigation and prevention of snow disasters in this region.

春季暴风雪经常发生在青藏高原非均质的下伏地表，造成经济和社会破坏。引发暴风雪的因素的强度尚不清楚。这项研究使用重新分析数据定量诊断了青藏高原上空大规模降雪事件的水汽，热力学和动力学条件。在这里，我们显示出冷涡，南支槽和子午线是有利的天气系统。降雪的特点是低层（-8.3×10 ^-7 g s ^-1 hPa ^-1 cm ^-2）和整层（^-4.5 ×10 ^-4 g s ^-1 cm ^-2）水分会聚，低层大气会聚和高水平发散（±3×10 ^-4 s ^-1），低水平正涡度（4.8×10 ^-4 s ^-1）和强垂直速度（− 4 Pa s ^-1）。尽管对流稳定的分层起到了抑制降雪的作用，但喜马拉雅山丰富的水汽和强烈的地形抬升以及下坡的风速收敛克服了这一问题，从而引发了2017年3月见证的大雪事件。这些诊断结果与WRF的结果完全一致模拟。我们的研究承认WRF在诊断分析中的重要性，加深了对进化机制的了解，并为准确预测青藏高原的此类事件提供了理论参考。这将有助于制定有效的可持续牲畜战略，以及减轻和预防该地区的雪灾。