Dear Tom,
Why don't we see lightning during snowstorms?
Cornelia Hatland, Evanston
Dear Cornelia,
Lightning does sometimes occur during snowstorms, and meteorologists have a
colloquial name for the phenomenon: thundersnow. It's a rare event, occurring in the
Chicago area only a few times in a given 10-year period.
The opaqueness of snowflakes and their sound-muffling fluffiness greatly limit the
distance that lightning can be seen or thunder heard during thundersnow events.
Typically during snowstorms, moist but relatively stable air flows gently up and over
colder air; it cools as it ascends and its moisture condenses into snow.
On rare occasions when a vigorous low pressure system is passing across the region
and it has drawn unstable air, usually of Gulf origin, into its wind system, the moist air
will surge into powerful rising currents that build into bona fide thunderstorms.
