What is Snow Mold?
Fresh snowfall can make for a beautiful winter scene, but too much snow and cold over a prolonged period of time (like, say, winter) can have a negative impact on your yard. The effects will be seen once spring arrives. You'll see bare or grey patches of blandness where you were hoping to see green grass.
Blame it on snow mold.
Snow mold is caused by a fungus that is active, underneath the snow, during the winter months. Snow mold can be caused by more than just heavy snow over the winter. Yards that have poor drainage can lead to soil that stays wetter for longer periods of time. This can increase the risk of snow mold.
The bad news is, once winter and spring arrive, there's not much to be done about snow mold. The lawn will not likely die, but it will be a bit ugly in those patchy areas. You can always re-seed and water the affected areas of the lawn. Start the recovery process by lightly raking the affected areas to loosen up the matted grass and allow new grass to grow.
To protect against snow mold, work needs to be done in the fall. Give your lawn a feeding of fertilizer in the mid-autumn, along with regular watering. Consider core aeration of your lawn at least once a year. This will help control thatch levels.
Another way to prevent snow mold is by mowing the lawn shorter than usual during the last mowing of the season.