jcjeant, I have been on a plane when the pilot ordered the cabin crew to their seats and said there will be some heavy turbulence. So a simple "watch out" is not even severe turbulence as I've ridden through going from the ONT to ORL or MSP. I'd not read too much into that warning to the cabin crew.
Now, there is a theory that they saw the storm ahead, thought they had a clear path, and discovered it was blocked at the far end by the grand-daddy storm. This supposes misuse of the radar due to, you guessed it, lack of training.