Thunderstorms

Severe weather cause major delays and tiresome worries, but being safe is the FAA main concern and following protocols and policy with what weather condition is acceptable to fly in. Thunderstorms are one of the most beautiful atmospheric phenomenon. For a pilot, however, thunderstorms are one of the most hazardous conditions they can encounter. All thunderstorms can produce severe turbulence, low level wind shear, low ceilings and visibilities, hail and lightning. Each of these hazards can be difficult to cope with; if all these conditions arrive at once, it can become disastrous. The FAA has mandates on the type of weather conditions that is acceptable for flight. Understanding basic thunderstorm formation and structure can help pilots make safe decisions weather or not to fly.

Three things are needed for a significant hazard to flight safety; moisture, lift and instability. There are also two sets of regulation when it pertains to flying in severe weather. For pilots it is understanding the visible flight rules that regulates flight in good weather and the instrument flight rules the permits for flying thru clouds and any other types of restricted visibilities such as a thunderstorm or a snow storm. Ultimately visibility plays a major role for the abundance of the flight regardless of what condition is being flown in. Thunderstorms and low visibility causes major concerns for the flight plan. FAA regulation code §91.157 Special Visual Flight Restriction and weather minimums. States that flight may operate under specific weather minimums with proper clearance from air traffic control and also if no ideation of visibility discrepancies exist.

http://www.quora.com/Why-does-weather-cause-air-traffic-delays-Why-cant-just-as-many-planes-take-off-and-land-in-the-rain