An EMB145 taxied off a taxiway on a snow covered ramp that had not been plowed after ATC confirmed that they were approaching the proper taxiway. The aircraft was shutdown and passengers bussed to the terminal.
Synopsis
An EMB145 taxied off a taxiway on a snow covered ramp that had not been plowed after ATC confirmed that they were approaching the proper taxiway. The aircraft was shutdown and passengers bussed to the terminal.
Narrative
As we were finished being deiced we completed after engine start checklist and requested taxi instructions. We were pushed from the gate it was dark and snowing and the ramp had not been plowed. ATC gave us taxi instruction: Taxi via A4 progressive to the runway; as I made a right turn from the gate what I think is A4 is completely covered with snow I stopped short and asked the First Officer to confirm with Tower that I am in fact approaching A4; Tower which is at my 12 o'clock asked to flicker the taxi light which we did and Tower says you are on it. I added a little taxi thrust and the nose gear exited the taxiway. Immediately I set the parking brake; did the parking checklist; notified Tower; Company Operations; Company Dispatch and coordinated to get the passengers to the terminal. Night conditions; snowing; poor visibility; ramp not plowed preventing from seeing the taxi line; and Tower confirming that we were approaching A4 Taxiway. Ramp needs to be clean to be able to see the taxiway line.
Second reporter narrative
Pushed back; de-ice and anti-iced aircraft; and got ATIS specifying that there was progressive taxi that morning due to weather conditions of 2;300 overcast; 1.5 miles visibility and light snow. The ramp and taxiways had not been plowed and were snow covered as it was early in the morning. We turned approaching where A4 was according to the airport diagram....The nosewheel rolled a few feet into the grass/snow. The main landing gear was still on the pavement and no injuries or damage to the aircraft. We coordinated with Airport Operations; Company Operations and ATC and got the ramp plowed and a bus to come get the passengers off the aircraft. We did our shutdown and terminating procedures and left the aircraft for the hotel upon direction of management. Conditions on the ramp was [that it is] not plowed and we could not see any markings. ATIS was publishing that they were giving progressive taxi; and we were using their guidance as well as the airport diagrams to the correct runway. Never ever ever ever taxi when the ramp isn't plowed.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.