The national home price index has become one of those gauges everybody watches even while knowing full well that real estate is local. One metro can be surging while another is rolling over, and sometimes that divergence exists within the same state. But the broader national trend right now is unmistakable. The market is weakening and continuing to weaken. Year-over-year appreciation has steadily decelerated, with really only one bright patch left in the country, the Midwest. Cleveland,...