Any thunderstorm is dangerous and should be avoided by at least 10 miles, but all thunderstorms are not created equal.
A supercell is a single long-lived thunderstorm characterized by a rotating updraft called a mesocyclone.
Here is a look inside a typical supercell showing its unique features, including the mesocyclone, and the forward-flank downdraft that can send gust fronts racing across the countryside, Supercell gust fronts regularly travel far enough for the parent supercell to be out of sight over the horizon. When a gust front crosses an airport, it can cause quick changes to wind speed and direction.
If you see a distant thunderstorm above the horizon with a dome-like top—as shown in the top illustration at the middle red arrow—it’s probably a supercell’s overshooting top. It could send a gust front across the airport where you’re planning to take off or land.