MBS just hit their lowest levels of the day--just barely--with 5.5 coupons down 5 ticks (.16) on the day and the same amount from the mid-day highs.  Most lenders published rate sheets before those highs, however, so they're not seeing more than 3 ticks (.09) of weakness.  That's usually not grounds for a reprice, but some lenders have a history of repricing simply because MBS have fallen enough from the highs, regardless of rate sheet print times.

Best way to use this alert: if you were already planning on locking today, there's no reason to wait.  If you weren't planning on locking today, there's no reason to panic.