Abstract: Based on conventional meteorological observations, satellite cloud imagery and radar data, a diagnostic analysis was conducted on the continuous three-day snowfall event that occurred at Kunming Changshui International Airport from January 26 to 28, 2025. The results indicate that this event was associated with a rare synoptic pattern characterized by a northern shear line without a southern trough. At the 700 hPa level, the conditions over the three days were as follows: the shear line pushed southward, combined with southwesterly flow ahead of a shortwave trough, the southwesterly flow ahead of the shortwave trough was accompanied by persistent cold air influence, the southwesterly flow ahead of the shortwave trough interacted with residual cold air. Throughout the three days, moisture conditions were insufficient, resulting in limited precipitation. Satellite cloud imagery showed that on the 26th, cloud layers developed at higher levels north of the shear line, with wavy cloud systems to the south; on the 27th, cloud systems developed at higher levels over central and western-southern Yunnan; and on the 28th, higher cloud development was observed in western to southeastern Yunnan. Doppler weather radar echo characteristics indicated frontal-triggered gravity waves on the 26th, while on the 27th and 28th, the areas ahead of the trough were dominated by stratiform clouds aligned in a southwest-northeast direction.