What is the general rule regarding avoidance of thunderstorms and what indicators would suggest that a thunderstorm is severe?

• A. Avoid severe thunderstorms by at least 20 nautical miles. Any storm with winds forecast above 50 knots and or contains hail greater than 3/4" is considered severe.
• B. Avoid thunderstorms by at least 50 nautical miles; severity defined by lightning.
• C. Always fly through thunderstorms; severity is not defined.
• D. Avoid thunderstorms only if visible; severity defined by rainfall.

Answer: (A)

Thunderstorm avoidance is about giving convective activity enough distance to stay out of hazardous conditions. The general rule is to stay at least 20 nautical miles away from thunderstorms to avoid severe turbulence, wind gusts, hail, and wind shear associated with those storms. When a storm is considered severe, it is typically defined by forecast surface winds of 50 knots or greater and/or hail at least 3/4 inch in diameter. These indicators signal that the storm’s updrafts and downdrafts can produce dangerous conditions beyond just heavy rain or lightning. Relying on lightning alone can be misleading, since a storm can be severe due to strong winds or large hail even if lightning density isn’t extreme. The other options misstate the distance, rely on lightning alone, or suggest flying through storms, which those guidelines specifically warn against.