RICHMOND, Va. (WTVR) – Many of you reported to us seeing the glow of white light in the clouds Thursday evening, followed by a rumbling sound like thunder. Your eyes and ears did not deceive you! That was lightning and thunder in a snowstorm. It’s called “thundersnow,” and it’s legit.
So how does this happen? We understand that lightning forms after an electric charge separation process in updrafts and downdrafts inside a convective system. When it’s cold enough, instead of rain reaching the ground, snow survives to the surface (like it did Thursday night in central Virginia). The upper-level dynamics just north of the low tracking through the Carolinas last night supported the instability necessary for that lightning to occur.
Many of you noticed the period of sleet that mixed in with the rain Thursday afternoon, and that indicated an above-freezing layer of the air above ground, followed by a sub-freezing layer as the precipitation fell down. That meant liquid precipitation falling melted, then froze as sleet, and then fell to the ground level. That temperature change overhead also enhanced that instability and charge separation process that can trigger lightning, especially as that vertical temperature profile became more complicated with the change-over to snow.