You can make more clearance in your fork by placing your wheel in the lowest possible position instead of the highest. Undo the quick release, lift the front end of the bike and let the quick release rest on the "lawyer tabs" at the bottom of the drop-outs. Clamp the quick release back down again, check that the tire is centered at the top of the fork and if not repeat the process. Now look to see if you have any more clearance above the tire. In some forks, this may give you a few mm extra clearance. As long as you keep the quick release nice and tight then the wheel shouldn't move back up. Obviously, also make sure that where the quick release clamps on the dropouts is still fully above the lawyer tabs and they are not interfering with the clamp surface of the wheel in any way.

I put full fenders and 25mm tires onto my 2007 Trek Madone by using this method last winter. For this winter, I have a cyclocross bike

EDIT: This technique might not be safe in some situations, but may be fine in others (read the comments below).