Here's the explanation I posted at 1330 on the SVXY board; obviously there was huge price movement immediately after this posted...
Tomorrow afternoon. the VIX futures expire.
March futures MUST converge with the spot. At Friday's close there was a $1.23 or 11% gap between spot at front month. That gap can be closed by the front month dropping to spot or spot rising to front month or somewhere in between.
Meanwhile, the back month (April) will take front month position Wednesday morning.
As I type, spot up 1.48, Mar up .62, Apr up .13 (1%)
As I type SVXY is down 1.3%
So, the gap that must close by tomorrow pm has closed to .39.
So many folks who are long VXX and her uberspawn, UVXY and TVIX, are bemoaning "how can the VIX be up 10% and our guys only move 1 or 2%.
It's because the VIX moved up to meet the front month.
The VXX and SVXY today have responded mainly to the movement of the Apr futures.