black ice on Sierra lakes
 

Camped in the Sierras 22-24, Desolation Wilderness. The Sierras don't
have snow (what's left is from a month ago storm), but there is plenty
of black ice above 8,000 ft. The ice 1 foot+ deep. Ice skating is no
skiing, but still.
They say the Gorge has managed to groom a 5K loop. Can't confirm.

black ice on Sierra lakes
 

http://www.mvsta.com/grooming2.html