Originally Posted by
Loren Pechtel
Turbulence does come out of the blue at times. However, it doesn't generally go from nothing to a big problem all at once. The pilots normally turn on the seatbelt sign at the first sign of turbulence, if you obey that the chance of being tossed around by it are very low.
I agree with the first sentence, but take issue with the second. You should always keep your seat belt fastened when you are seated, even if the sign says you don't have to.
Those of us who are CH 9 junkies on UA know that pilots are always asking for ride reports if they suspect to encounter turbulence, but there have been many times where ATC has given a flight a clean forecast, and yet turbulence has been abruptly encountered later on in the flight.