Watch out for the black ice

We had about half an inch of snow last night, but it melted a lot during the day, and the Parkway path was clear of snow. However, when I left home for my run, the shade temperature was 30 (F) (I ran in the late afternoon), and water from the melted snow was freezing in shady spots. Most of the path had direct sun, and the water hadn't froze yet.