Originally Posted by Dash8Pilot

Both Southwest and Horizon have Heads-up Guidance System guidance in their aircraft. That allows takeoff minimums of 600 RVR at many airports, and down to 300 RVR at a few (very doubtful that RNO is one of these). With HIRL, CL, RCLM, and a functioning localizer on 34L, I'm guessing they have 600 RVR minimums (anyone at Southwest or Horizon feel free to correct). It's also entirely possible with the way that visibility can fluctuate that when they moved into position they were able to see at least 600 ft.