Mortgage rates surged higher at a rapid pace for the second time this week. Taken together, the jump is the biggest of its kind since the big rate spike in September, and one of only a handful of weeks in the past 3 years where lenders are quoting rates that are 0.25% higher than the previous week.
Progress on the US/China trade deal is the key culprit behind the volatility, but not the only factor. In general, the bond market (which dictates rates) has been doing so well for so long that risks of a bounce have been increasing simply due to doubts as to how long the good times could continue to roll. In market jargon, these motivations are referred to as "technical."