Narrative:

Crew taxied out for deice on the opposite end of ramp. Crew accomplished all flows and checklists relating to deice with engines running. After given the all clear signal from deice truck; sic contacted metering and advised ready to taxi. We were instructed to switch to ground where we received taxi instructions to taxi to runway via whiskey. After taxiing a short bit; ATC called looking to amend taxi instructions as the ILS critical area was active; given the heavy snow and low visibility. Sic was distracted copying instructions as per aom/fom. In attempting to taxi onto whiskey; I taxied the aircraft toward the blue lights on the parallel taxiway. Unfortunately; the clear area of the ramp and grass blended together with snow cover and I taxied off the ramp with the nose gear and the left main gear.once I felt the slump on the left side; I immediately recognized the aircraft had departed the ramp and was on the grass. We stopped the aircraft; advised ATC and performed a normal shutdown. I then called maintenance for guidance on how to proceed.the aircraft was left chalked and marked with cones before leaving the airport. I would suggest both pilots be required to keep eyes outside in low light foul weather ground operations until on a lighted taxiway; or ramp. In addition; specific to this airport; I would recommend reflectors; or lights on the ramp edge as a snow covered surface is very difficult to discriminate between ramp and grass at night.

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Original NASA ASRS Text

Title: A CE-560 Captain taxied the left and nose gear off a ramp onto the adjacent grass at night with moderate snow in limited visibility while the First Officer copied a new taxi clearance. The ramp and snow covered grass blended together.

Narrative: Crew taxied out for deice on the opposite end of ramp. Crew accomplished all flows and checklists relating to deice with engines running. After given the all clear signal from deice truck; SIC contacted metering and advised ready to taxi. We were instructed to switch to ground where we received taxi instructions to taxi to Runway via Whiskey. After taxiing a short bit; ATC called looking to amend taxi instructions as the ILS critical area was active; given the heavy snow and low visibility. SIC was distracted copying instructions as per AOM/FOM. In attempting to taxi onto Whiskey; I taxied the aircraft toward the blue lights on the parallel taxiway. Unfortunately; the clear area of the ramp and grass blended together with snow cover and I taxied off the ramp with the nose gear and the left main gear.Once I felt the slump on the left side; I immediately recognized the aircraft had departed the ramp and was on the grass. We stopped the aircraft; advised ATC and performed a normal shutdown. I then called maintenance for guidance on how to proceed.The aircraft was left chalked and marked with cones before leaving the airport. I would suggest both pilots be required to keep eyes outside in low light foul weather ground operations until on a lighted taxiway; or ramp. In addition; specific to this airport; I would recommend reflectors; or lights on the ramp edge as a snow covered surface is very difficult to discriminate between ramp and grass at night.

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.