After a snowfall of about 2 " I noticed one brick in the center of my chimney that was wet. It's the only brick that is wet and it is about half way up the chimney and on the inside. Is this common in the case of a flashing leak around the chimney as it goes into the roof, or a leak in the concrete chimney cap? There is no spark arrestor or other device that prevents the snow coming down the chimney. To have the leak restricted to only one central brick seems pretty odd. Any words of wisdom would be appreciated?