Couple years back they opened the 21 only because of 5 inches of natural. I'm sure there must of been one later then that, just can't quite grasp it.

I dug through some past DCSki articles and found some late opening dates.

In 1998, Whitetail opened on Saturday, December 26.  [http://www.dcski.com/articles/499]

In 1999, Whitetail opened sometime around December 20 or 21.  [http://www.dcski.com/articles/611]

In 2001, Whitetail opened on Monday, December 26.  [http://www.dcski.com/articles/692]

After a quick search, I couldn't find any references to Whitetail not opening until January, although there have been instances where resorts barely opened and then closed, not reopening until well into January.  For example, in the 2006-2007 winter season, Whitetail briefly opened before Christmas thanks to cold temperatures the first two weeks of December, but then, as DCSki reported, "the cold air swirled away and disappeared from the region, as if frightened away by an unseen force -- global warming, or perhaps El Nino, theorized many skiers as they looked forlornly as quickly-melting slopes."  By January 8, 2007, Whitetail still hadn't reopened.  It reopened sometime around January 13, 2007.  [http://www.dcski.com/articles/958]

I had dec 30, 2011. as one late open. Actually this seems the latest.  Thank goodness for automated snowmaking. 

pretty even opens accross lat nov, early, mid late dec.  I took care of any major chores items now and left Jan and feb pretty open and flexible. Will still get 25 days /nights in.