Question
A few days ago when I mowed the lawn I noticed several spots of grass that had turned a whiteish grey color. Looking closer there were tons of little white bumps on the grass. This morning when I looked outside the white patches have turned to black and the little bumps are still white.  What could this be and how can we fix it???
Thanks!!!

Answer
From your description, the symptoms sound like powdery mildew (PM) or smut and that you have a winter turf, like bluegrass, rye or fescue.The black color is confusing. PM spreads so quickly that the result is dramatic.  To pinpoint the problem, ask your local ag agent for a tissue analysis of the turf.
Both are brought on by heavy watering or rain, fertilization, and cool temperatures.
A systemic fungicide can be used for smut, but check with your local ag agent about what type and when.  PM can not be treated effectively.
Raise the lawn mower setting.  Do not overfertilize.  When watering, water deeply, not just sprinkling to dampen leaves.  Raise pH to 6.0 plus.  Consider pruning trees and shrubs to let sunlight in and increase air circulation in the shady spot, or plant a groundcover there.  Change the micro-environment in your favor.
You can wait this out and reseed in the fall, ugly as it is.
Best of luck.