I generally agree with this answer but would note that under Washington law there is essentially a presumption that the driver of the car that rear-ends another car is negligent and liable (Miller v. Cody, 41 Wn.2d 775, 252 P.2d 303 (1953)). If you can establish that the other driver's action consituted "unexpected behavior" (which will be determined by a jury in all likelihood), then you may have a defense. As a matter or practicality, I am afraid that most jurors would find you liable based on the fact that Washington law requires that all drivers maintain a "proper lookout" for other cars and operate their vehicle in a way and at a speed that is reasonable under the circumstances. Based on your description of the corner and accident, I suspect that a jury would conclude that you should have made your turn at a speed low enough to have allowed you to stop before hitting the other car.
Agree with Mr. Gilvert.