On a typical day, VXX captures about 40-50% of the VIX move. A day like today on the heels of a long weekend tends to see the net move of the VIX skew upwards. That's because traders lower bids of actual index options ahead of long weekends so as to not needlessly pay extra time decay. So it's entirely possible that VXX gives a truer picture of the volatility move today.
If that's the case, then it's a rather ugly day as VXX has declined 5.5% as I type, translating into maybe a 12% dip in the VIX. That's much uglier than the 1.75% dip on the screen.
It's also possible that it's another step in the VIX futures marts just giving up on the hope for increased volatility going forward. Feb. futures have a $4 premium, still kind of high but $1 lower than last week.
Also don't forget Jan. VIX expires tomorrow, so be on the lookout for lots of pointless OTM put volume in SPX and perhaps an unusual settlement price (they're suggesting about 18 now).
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