A leading edge of gusty surface winds from thunderstorm downdrafts.

• A. Microburst
• B. Gust Front
• C. Wind Shear
• D. Turbulence

Answer: (B)

When a thunderstorm sends air downward (a downdraft) and that air hits the ground, it spreads out and moves outward as a boundary of gusty winds. This advancing edge of surface outflow is called the gust front. It marks the leading edge where the storm’s outflow affects the surface, often bringing a sudden gust and a wind shift as it passes.

The other terms describe different things: a microburst is the strong downdraft itself reaching the surface and spreading out locally, not the boundary ahead of the storm; wind shear refers to how wind changes with height or across the direction of travel, and turbulence is irregular, chaotic motion within the air. The description matches the gust front—the boundary of outflow at the surface.