Be very careful with patterns! The size on a sewing pattern has NOTHING to do with the size of store bought clothing. Measure the largest part of your body, (on me the big ole hiney) and compare with the measurments on the back of the pattern. It would be awful if you searched for a pattern and made a coat that would not fit.
You may want to consider a swing coat rather than a stadium coat. I made a swing coat 19 years ago and still wear it. I get compliments on it everytime I do. I have even had men tell me they like my coat. (Receiving compliments is NOT on my daily adgenda, so I remember them).