GM-GMC: screeching brakes after overnight set in rain,lowtrac lite comes on-forward and reverse, unfortunate side effect, overnight rain

Question

 when car sets overnight and it rains, low trac lite comes on and with car in motion brakes screech and rattle like the car going forward seems to lock up and nosedive. After continuing on the breaks warm up and it's ok till the next overnight rain.
 Mechanic reworked brakes, ceramics etc.
 The noise is frightening and unnerving to say the least.
             Any advice for me?    Thank you!!

Answer
I would say you have two seperate concerns.  The first being the noise from the brakes, which is an unfortunate side effect of most ceramic braking material.  They make noise etc until they heat up.  They have fantastic wear charecteristics, but are noisey until warm.  If it is too loud for your liking you may need to switch to a softer braking material.  Secondly the low trac light may come on as a result of a faulty or failing abs sensor or as a result of the brakes grabbing.  I would suspect the second is the case.  If the brakes grab or the tires lock up, even momentarily, the abs module see's it as a low traction concern and will cycle the abs ( the rattling noise).  Only real solution would be to swap the pads for a semi metallic or other type of brake pad.  If I knew what type of car etc I could make a slightly better recommendation.  Your mechanic should take car of you if you are not satisfied.
Hope this helps.