Besides the fact that the branch prediction may slow you down, a sorted array has another advantage:
You can have a stop condition instead of just checking the value, this way you only loop over the relevant data, and ignore the rest.
The branch prediction will miss only once.
// sort backwards (higher values first), may be in some other part of the code
std::sort(data, data + arraySize, std::greater<int>());
for (unsigned c = 0; c < arraySize; ++c) {
if (data[c] < 128) {
break;
}
sum += data[c];
}