Today the market experienced a divergence in the typical negative correlation between SPY and short-dated VIX, with SPY +0.65%, VIX +1.1%, and front month VIX futures +1.3%. This often happens when the SPY hits new relative highs (a 5-year high for SPY in this case) as traders start buying protective puts to lock in gains, and around options expiration days (tomorrow).
From here we're likely to see more buying of short-dated VIX over the next few days as it continues to adjust, as I wrote about two days ago. This would result in a lower XIV and higher VXX. I don't typically recommend buying VXX and holding it overnight, so at this point I'm just looking for my signal to buy back XIV at a lower price.