Learned this a couple of years ago. You can Advance (or Assault Move) into an open ground or other non-Concealment terrain hex and maintain Concealment as long as there is a Hindrance that would negate the FFMO for a potential firer (other SRs notwithstanding, i.e., snow camouflage, etc.). I don't believe LV hindrances (mist, dust, twilight, etc.) count towards negating FFMO, they only modify fire at the target.
