Approaching thunderstorm with lead gust front.
Rain-cooled air from the storm moves out ahead of the storm.
It ploughs under the warm moist air forming a flat"shelf cloud."
Image ID: nssl0041, NOAA's National Severe Storms Laboratory (NSSL) Collection Photo Date: 1982 Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)
