Well, according to the Washington State Department of Health - don't go rushing out to the store to buy potassium iodide.  There is no need!  The Department of Health says not to expect any

 significant levels of radioactivity in our state, and there’s no health risk. Japan is thousands of miles from our state, and if radioactivity from the reactors there is released to the upper atmosphere it would be thinned-out by the winds before it could reach us. Read more HERE.