Conditions were optimal for a brief, mild hailstorm in Spring Valley on Monday, February 10. A series of rapidly moving clouds headed east had caused off-and-on rain throughout the day. At 4:19 p.m., a sudden loud "tinking" sound was heard as the hailstones hit the ground. The hail dropped from the leading edge of a fast-moving and tall thundercloud.
Hail is formed when a cloud's frozen water droplets are blown back up into the cloud; they become larger when more water attaches to them. At the top of the updraft, they fall again, only to be blown back up into the cloud again. When they become heavy enough, they drop suddenly.
As the center of the thunderhead moved east over Spring Valley, the hail ceased and a downpour of rain occurred, quickly soaking and melting the slushy white hailstones on the ground. By 4:49 p.m., the thunderhead had passed and could be seen towering in the east, surrounded by clear blue sky.