The Birkie hasn’t posted this to their homepage, and buries it several levels down, but here is the latest information for trail closings before the race (current as of 9 a.m. Thursday):

• 10 a.m.: Classic Course Closed
• 4 p.m.: Skate Course Closed north of OO
• 6 p.m.: All Trails Closed

The main caveat here is that there will likely be 2–4 inches of new snow on the trail falling on Friday. So the Birkie will have to set new tracks during the storm for the classic, and will likely be out packing the new storm. So if you do ski before the official closures, watch for grooming machines on the trails. It is always possible that the Birkie will close the trails earlier, although with ample snow (it’s cold—temperatures bottomed out this morning at -15) and new snow falling, there is no particular reason to do so other than to clear skiers off the course to allow them to pack the snow more easily. Snow should start in the morning on Friday and fall lightly during the day (1/3 to 1/2 inches per hour) with temperatures in the low 20s before tapering around midnight. There may be very light snow (1/2 inch) during the race.

The entire course will get a full once-over (or perhaps more-than-once-over) before the race on Saturday morning.