If you haven't done so, your lawn needs to be cut back to about an inch or, an inch and a half. You also need to clear it if all debris, leaves, twigs, etc. All this will prevent issues when the snow melts and spring returns. It is also a good time to add a little extra, high-quality grass seed to you turf to help it come the new year.
Leaving grass long will enhance the probability it will be matted with excess thatch once the turf is visible once more. Cutting the grass back will also prevent snow mould and damage from critters like voles who love to tunnel their way under the snow while leaving tracks in your lawn.
This winter is expected to be quite severe and the opposite of last year's mild conditions.
So, do your self a favour and your grass as well. When the days become shorter, so should the length of your lawn. Otherwise, come spring you may be in for a rude awakening.