Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Weather / Turbulence; Ground Incursion Taxiway
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors; Weather
When arriving in BOI we were cleared for a Cat 3 approach. The visibility was reported at 1200 RVR with freezing fog and temperature -2. As we were shooting the approach; I elected to fly solid bug even though we had no ice detected. Once we entered the clouds I didn't want to be distracted by a possible Ice Detect message near the ground. But after passing 500 ft. an Appch Warn message appeared so I missed the approach. After the missed approach; I was trying to figure out what was not right and it occurred to me that I didn't have the Ref Speed switch on. So I selected it on and came in for another approach. By this time the weather had gone down to 1000 RVR. We shot the approach and landed. During the rollout the visibility was pretty good and as I was braking and slowing down I plainly saw taxiway E and I made the turn at E. After I had made the turn; tower told us to continue to the end of the runway and turn off at the end. We told them we had already turned off at E. They proceeded to have us cross the left runway at E and continue to parking. It occurred to us that low vis ops were in effect and we should have gone to the end of the runway to follow the lead off lights but tower didn't tell us to go to the end until we had already gotten off at E. The main cause of this was being distracted by the missed approach and trying to figure out why we got the Appch Warn. After we figured it out; the weather had gone down to 1000 RVR and it didn't occur to us about rolling out to the lead off lights. I was more concerned about shooting a successful approach. Another thing that didn't help was that company had shot an approach in front of us and we heard them get off at E. But the weather was 1200 RVR when they landed. I think we were expecting to be able to do the same thing based on what they did. After researching a little we found in the Flight Manual a cautionary note saying that I didn't need to proactively fly at solid bug in anticipation of getting ice. I could've flown open bug if practical and if we did get an ice detect message to not destabilize the approach presumably by increasing speed to solid bug and selecting the Ref Speed switch on when below 500 ft. If I had done this originally I wouldn't have needed to miss the approach the first time. I learned to pay attention to RVR values as they pertain to roll out and taxing; not just landing. 1200 RVR and below is a clue to remember that low vis ops are in effect even if tower doesn't say anything about it and to anticipate looking for lead off lights.
Air carrier Captain reported turning off the runway at the incorrect exit point after landing during low visibility conditions.