Narrative:

During extremely low visibility; we were directed to taxi from the ramp via E5 to east. Because of the low visibility I taxied at an extremely slow speed and directed the first officer to commit all of his attention to helping me to find the appropriate taxiways. All I could do was to compare the taxi chart to what I was directed to do. Both the first officer and I agreed that we were to take the first 90 degree [right] turn off of the ramp. All I could see was a few feet of the yellow taxi line in front of the nose of the aircraft. When I came to the first divergent taxi line to the right; I took it. As soon as I completed the 90 degree right hand turn; something didn't feel right. I slowed to a stop and discussed it with the first officer. We surmised that we had turned early and were actually parallel to east on the ramp. We contacted ground to appraise them of the situation and they concurred that we had turned too soon and were parallel to east. There was no conflict or danger where we were and ground told us to continue the taxi and join east at E4 which we did. The remainder of the taxi out was uneventful. Poor visibility and unfamiliarity with the facility.I take responsibility as the captain any time the airplane is not where it's supposed to be. Two things could have helped me to do a better job: better signage for the conditions at hand. I could see the taxi line and that was it! Even if there had been something painted on the concrete at the line that I took on to the ramp depicting that line as going to the ramp; I would not have made this mistake. Secondly; I religiously read every word on company charts for every ramp on which I operate. Had there been a note to the effect of 'in low visibility conditions when exiting the ramp; do not mistake the first turn to the right for taxiway east' I would have been aware of the potential for making the mistake I made and do not believe I would have missed it.

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Original NASA ASRS Text

Title: Air Carrier flight crew reported taxi confusion at PDX in low visibility conditions.

Narrative: During extremely low visibility; we were directed to taxi from the ramp via E5 to E. Because of the low visibility I taxied at an extremely slow speed and directed the First Officer to commit all of his attention to helping me to find the appropriate taxiways. All I could do was to compare the taxi chart to what I was directed to do. Both the First Officer and I agreed that we were to take the first 90 degree [right] turn off of the ramp. All I could see was a few feet of the yellow taxi line in front of the nose of the aircraft. When I came to the first divergent taxi line to the right; I took it. As soon as I completed the 90 degree right hand turn; something didn't feel right. I slowed to a stop and discussed it with the First Officer. We surmised that we had turned early and were actually parallel to E on the ramp. We contacted Ground to appraise them of the situation and they concurred that we had turned too soon and were parallel to E. There was no conflict or danger where we were and ground told us to continue the taxi and join E at E4 which we did. The remainder of the taxi out was uneventful. Poor visibility and unfamiliarity with the facility.I take responsibility as the Captain any time the airplane is not where it's supposed to be. Two things could have helped me to do a better job: Better signage for the conditions at hand. I could see the taxi line and that was it! Even if there had been something painted on the concrete at the line that I took on to the ramp depicting that line as going to the ramp; I would not have made this mistake. Secondly; I religiously read every word on company charts for every ramp on which I operate. Had there been a note to the effect of 'in low visibility conditions when exiting the ramp; do not mistake the first turn to the right for Taxiway E' I would have been aware of the potential for making the mistake I made and do not believe I would have missed it.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.