Mortgage rates spiked in a big way today, bringing some lenders to the highest levels in nearly 7 years (you'd need to go back to July 2011 to see worse).  That heavy-hitting headline is largely due to the fact that rates were already fairly close to 7-year highs, although today did cover quite a bit more distance than other recent "bad days." 

In fact, today covered more ground BECAUSE we were so close to those highs.  This has to do with trading strategies that are based on math and momentum.  The high rates from 3 weeks ago were the same as the high rates seen in 2013/2014.  That reinforced a magic line in the sand that--if crossed--was likely to result in extra momentum moving through to the other side.  True to the formula, today was the first official break of those 2013/2014 highs in terms of 10yr Treasury yields (a benchmark for longer-term rates like mortgages) and as soon as that break occurred, it quickly turned into the heaviest day of selling in months ("selling" bonds = higher rates).

What should you do about it?  Days like today are tough.  There are plenty of past examples of such days serving to exhaust near-term upward momentum in rates.  In other words, rates go so high, so quickly, that they end up improving on the following day.  Indeed that's possible, but it's not any more likely than more dire options.  Just as many past examples suggest locking a rate sooner vs later, or doing everything in your power to get an existing loan closed before the lock expires.