Meaning of phrase in a journal

"less certain the farther" is not really a phrase here. A number of words have been omitted, and the second part of the sentence should be interpreted and (the conflict prediction) is less certain the further in advance the (aircraft trajectory) prediction (is), however. Another paraphrase would be and the farther in advance the aircraft trajectory prediction is, the less certain the conflict prediction is.

The sentence refers to two predictions, and it is not totally clear which prediction is meant by the second-last word. While I believe that explicitly using the word "prediction" here implies that it is not the same prediction as mentioned immediately prior, it is possible that the paraphrase should be and the conflict prediction is less certain the further in advance it is.