The aerosynoptic situation on May 9, 2025, was influenced by a young cyclone moving from the Novgorod to the Yaroslavl region, with clouds approaching to Moscow at speed of 25–30 km/h. During the morning hours (6:00–12:00 AM) the Moscow region experienced variable cloudiness with cloud top of 3–4 km (Fig. 1) and with precipitation up to 1 mm/h in some areas.

The air temperature in Moscow and the Moscow region ranged from +4 to +8°C, with the zero isotherm at altitude of 800 m. A westerly wind of 2–4 m/s was observed. Based on the meteorological situation and in accordance with the flight plan, a Roshydromet Yak-42D laboratory aircraft (number 42440) was launched from Chkalovsky airport at 4:00 AM Moscow time to conduct atmospheric sounding and to test silver iodide and liquid nitrogen seeding to the west and northwest of Moscow. At 4:15 and 4:30 AM Moscow time, two An-12 aircraft (board numbers 14 and 94396) were lifted into air at the area bounded by azimuths of 250–340 degrees and ranges of 100–180 km from Moscow to monitor clouds and conduct seeding with solid carbon dioxide, cement packages and liquid nitrogen. Between 7:00 and 9:00 AM, seven An-26 aircrafts were lifted in air to conduct operations in area near Moscow region. At 10:00 AM, ten aircraft were in the air. Due to increasing cloud cover moving toward Moscow, between 9:30 and 12:30 Moscow time, six Russian Aerospace Forces aircraft conducted seeding with powdered reagents at ranges of up to 120 km west and southwest of Moscow. This active intervention reduced the cumulus cloud intensity over Moscow from 8-9 to 3-4 points, preventing the potential development of convective clouds. During the day, a diffuse cold front approached to Moscow from the west, increasing cloud cover to 8-9 points, with its upper boundary at an altitude of 3.5-4 km (Fig. 2). The air temperature was +8 to +10°C, with westerly wind of 3-5 m/s.

As these cloud zones, producing precipitation rates up to 1 mm/h, began to threaten Moscow from 12:00 to 18:00, 10 aircraft were lifted again into air, conducting intensive interventions with all types of reagents from 1:30 PM. According to the Customer’s instructions, aerial work was completed at 10:00 PM. A total of 20 aircraft flights were conducted on May 9, 2025. These extensive interventions prevented precipitation in Moscow city.