Lahiri, who had a one-under 70 on first day, added a 67 on second and birdied the only hole he played in the third round before fading light ended play.
Lahiri is now six-under for 37 holes and will play 35.
Leader Dustin Johnson (66-66) could become World No. 1 if he wins and Jason Day finishes lower than a two-way tie for third.
Day (70-70) is tied-53rd at one-under after 41 holes.
Pat Perez (67-66) and Cameron Tringale (69-64) are tied-second at nine-under 133, while three players are tied at seven-under 135.
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The globe-trotting Lahiri, who has already made on two-week trip to Asia and will make another one-week visit to Delhi for Hero Indian Open, a title he won in 2015, has been handling his Transatlantic travels well.
Tied-19th at Dubai, he was tied-7th in Malaysian Championships and is now tied-7th midway through the Genesis Open at the Riviera.
Lahiri had five birdies and his only bogey came late in the evening on the par-5 17th, where he missed a shot par putt. He had birdies on first, third, sixth, 10th and 13th.
Lahiri, who had a tough start as the weather meant start-stop-start on first day itself, said, "We had four delays and it took us an hour and a half for two and half holes. But I didn't have to play much yesterday (Friday) when it was the hardest. I have had 4 am wake up calls on Thursday and today (Saturday), but it probably evens out in the end.
"I have played in Asia, in Malaysia and Singapore, where you can spend days sitting out and play late evening. I think after the rains, the course was playing longer, maybe even 500 yards, but softer. The roughs were up but with crowds trampling on it, you could get a decent lie."
"I am feeling good and positive. I got in a few birdies (in the second round) and have generally been feeling good about my game last couple of weeks. I did have some unforced errors but lot of bogeys in first 36 holes. And yes, I am ready for 35 holes."
Apart from Lahiri, there is another player of Indian origin, Sahith Theegala, who is making his PGA Tour debut and with a start of 67-73 he is tied-43rd and had made the cut.
Lahiri met him briefly, and said, "He hasn't played much amateur golf in India, so he's been a bit under the radar. But obviously, he's a really good prospect.