Narrative:

Departing for ZZZ; we received departure WX indicating that ZZZ had 1/2 mi visibility; snow; and gusty wind conditions. En route; the ATIS indicated 3/4 mi visibility; 6 mi broken; light snow; and winds of 320 degrees at 10 KTS gusting to 16 KTS. I elected to fly the ILS CAT ii approach due to the gusty winds; low visibility; and snow conditions at ZZZ. We did our landing data with wet/fair and had sufficient stopping margin for minimum braking. We briefed the approach as a captain flown CAT ii approach and we briefed the taxi route to gate as exiting the runway on either high speed taxiway xx or xy north on xz; a sharp right turn onto taxiway xw; then a slight left to the gate. In descent we received updated WX of winds 320 degrees at 11 KTS; 1/4 mi visibility; heavy snow; VV004; and braking action fair. We asked for the RVR and receive runway xx; RVR: touchdown 3000 ft; midpoint 3000 ft; rollout 2800 ft. We received vectors to the ILS xxl; flew the ILS xxl CAT ii approach; and made an uneventful landing. We exited the runway at high speed taxiway xx and turned northbound on taxiway xz. Heavy snow was falling and had evidently been accumulating for a while. All taxiway markings and centerline lights were covered with snow and there were no visible aircraft tracks from preceding aircraft. The only visible taxiway indications were the raised taxiway edge lights on the sides of the txwys and we used these lights as reference to taxi. Also; falling snow and wind blown snow made the visibility a challenge even with the landing lights on. We were instructed by ground control to taxi xz; xw; to the gate. We both verified the route against our airport diagram. The route matched our briefed taxi plan and we slowly proceeded northbound on taxiway xz. We monitored our progress as we proceeded northbound and noted crossing runway xx that it was completely covered with snow. After crossing xx; we began looking for the approximately 120 degree right turn onto taxiway xw to our right. The snow was very deep on the taxiway at this point and we saw ahead and to our right what appeared to be the raised lights of taxiway xw on the right and as we got closer we saw what appeared to be taxi tracks on the taxiway toward the ramp. We slow the aircraft to less than 5 KTS and agreed that this was taxiway xw to our right. I began the right turn and 1/2 way through the turn; ground called and said that we'd missed our turn and to continue north for a 180 degree turn. The first officer answered that we were in the turn. Confused by the radio call; I attempted to brake the aircraft to a stop. The aircraft slid on the snow with poor braking. I centered the nosewheel and as we slid to a stop we felt the nosewheel drop. Assuming that the nosewheel was off the taxiway; we informed ground control and company. We requested assistance from operations; we started the APU; and shut down the engines. We coordination with company through ZZZ operations and dispatch for assistance to get transportation for our passenger and equipment for getting the aircraft unstuck and to the gate. I informed the passenger that we were stuck and we were making arrangements to get them to the gate. Operations brought out a set of air stairs and we deplaned the passenger through the rear entry and transported them to the terminal via bus. We then worked with a mechanic to evaluate the aircraft and see what we could do to get the nosewheel back on the taxiway. He evaluated the aircraft and said the aircraft was undamaged. He then proceeded to dig out the snow around the nosewheel so we could pull the aircraft out once equipment arrived. After 6 hours of work involving snowplows; a large tow truck; and one of our tugs; we rode the brakes and the aircraft was towed to the ramp by operations personnel. After the heavy snow stopped; we began to see our surroundings more clearly. We realized that taxiway xw had been covered with heavy snow as we crossed it and as a further complication; 4 of taxiway xw lights; on the north side of taxiway xw were it intersects with taxiway xu; were not light at all -- but rather unlit blue poles. This combination of no edge lights on the north side of taxiway xw and heavy snow made taxiway xw appear not to be a taxiway in the heavy snow conditions. What we perceived to be the taxiway xw lights were really cargo ramp edge lights on the right (north) side and the few remaining lit taxiway xw lights on the left (south) side. The perceived aircraft taxi tracks were tufts of grass in the snow in a raised area of earth running parallel to taxiway xw. We were fooled by false cues that showed us both what we expected to see. The amount of snow at ZZZ made correctly identing taxiway xw very difficult with an absence of raised lights on the north side of the taxiway. In hindsight; I would completely stop the aircraft and ask for the assistance of a follow-me or a tug to the gate. Supplemental information from acn 777494: I began day 3 of a 4-DAY reserve block in our departure city. Rertes the prior day led to a 16 hour 32 min duty day with 9 hour 3 min rest. Despite the long day and short rest period; I felt adequately rested for the day ahead which was to be 2 legs and 2 deadheads.

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Original NASA ASRS Text

Title: AN ACR CREW REPORTS BEING UNABLE TO SEE TXWY EDGES AND TAXIING THE NOSE WHEEL OFF A TXWY COVERED IN SNOW. ACFT SHOULD HAVE BEEN TOWED TO THE GATE.

Narrative: DEPARTING FOR ZZZ; WE RECEIVED DEP WX INDICATING THAT ZZZ HAD 1/2 MI VISIBILITY; SNOW; AND GUSTY WIND CONDITIONS. ENRTE; THE ATIS INDICATED 3/4 MI VISIBILITY; 6 MI BROKEN; LIGHT SNOW; AND WINDS OF 320 DEGS AT 10 KTS GUSTING TO 16 KTS. I ELECTED TO FLY THE ILS CAT II APCH DUE TO THE GUSTY WINDS; LOW VISIBILITY; AND SNOW CONDITIONS AT ZZZ. WE DID OUR LNDG DATA WITH WET/FAIR AND HAD SUFFICIENT STOPPING MARGIN FOR MINIMUM BRAKING. WE BRIEFED THE APCH AS A CAPT FLOWN CAT II APCH AND WE BRIEFED THE TAXI RTE TO GATE AS EXITING THE RWY ON EITHER HIGH SPD TXWY XX OR XY N ON XZ; A SHARP R TURN ONTO TXWY XW; THEN A SLIGHT L TO THE GATE. IN DSCNT WE RECEIVED UPDATED WX OF WINDS 320 DEGS AT 11 KTS; 1/4 MI VISIBILITY; HVY SNOW; VV004; AND BRAKING ACTION FAIR. WE ASKED FOR THE RVR AND RECEIVE RWY XX; RVR: TOUCHDOWN 3000 FT; MIDPOINT 3000 FT; ROLLOUT 2800 FT. WE RECEIVED VECTORS TO THE ILS XXL; FLEW THE ILS XXL CAT II APCH; AND MADE AN UNEVENTFUL LNDG. WE EXITED THE RWY AT HIGH SPD TXWY XX AND TURNED NBOUND ON TXWY XZ. HVY SNOW WAS FALLING AND HAD EVIDENTLY BEEN ACCUMULATING FOR A WHILE. ALL TXWY MARKINGS AND CTRLINE LIGHTS WERE COVERED WITH SNOW AND THERE WERE NO VISIBLE ACFT TRACKS FROM PRECEDING ACFT. THE ONLY VISIBLE TXWY INDICATIONS WERE THE RAISED TXWY EDGE LIGHTS ON THE SIDES OF THE TXWYS AND WE USED THESE LIGHTS AS REF TO TAXI. ALSO; FALLING SNOW AND WIND BLOWN SNOW MADE THE VISIBILITY A CHALLENGE EVEN WITH THE LNDG LIGHTS ON. WE WERE INSTRUCTED BY GND CTL TO TAXI XZ; XW; TO THE GATE. WE BOTH VERIFIED THE RTE AGAINST OUR ARPT DIAGRAM. THE RTE MATCHED OUR BRIEFED TAXI PLAN AND WE SLOWLY PROCEEDED NBOUND ON TXWY XZ. WE MONITORED OUR PROGRESS AS WE PROCEEDED NBOUND AND NOTED XING RWY XX THAT IT WAS COMPLETELY COVERED WITH SNOW. AFTER XING XX; WE BEGAN LOOKING FOR THE APPROX 120 DEG R TURN ONTO TXWY XW TO OUR R. THE SNOW WAS VERY DEEP ON THE TXWY AT THIS POINT AND WE SAW AHEAD AND TO OUR R WHAT APPEARED TO BE THE RAISED LIGHTS OF TXWY XW ON THE R AND AS WE GOT CLOSER WE SAW WHAT APPEARED TO BE TAXI TRACKS ON THE TXWY TOWARD THE RAMP. WE SLOW THE ACFT TO LESS THAN 5 KTS AND AGREED THAT THIS WAS TXWY XW TO OUR R. I BEGAN THE R TURN AND 1/2 WAY THROUGH THE TURN; GND CALLED AND SAID THAT WE'D MISSED OUR TURN AND TO CONTINUE N FOR A 180 DEG TURN. THE FO ANSWERED THAT WE WERE IN THE TURN. CONFUSED BY THE RADIO CALL; I ATTEMPTED TO BRAKE THE ACFT TO A STOP. THE ACFT SLID ON THE SNOW WITH POOR BRAKING. I CTRED THE NOSEWHEEL AND AS WE SLID TO A STOP WE FELT THE NOSEWHEEL DROP. ASSUMING THAT THE NOSEWHEEL WAS OFF THE TXWY; WE INFORMED GND CTL AND COMPANY. WE REQUESTED ASSISTANCE FROM OPS; WE STARTED THE APU; AND SHUT DOWN THE ENGS. WE COORD WITH COMPANY THROUGH ZZZ OPS AND DISPATCH FOR ASSISTANCE TO GET TRANSPORTATION FOR OUR PAX AND EQUIP FOR GETTING THE ACFT UNSTUCK AND TO THE GATE. I INFORMED THE PAX THAT WE WERE STUCK AND WE WERE MAKING ARRANGEMENTS TO GET THEM TO THE GATE. OPS BROUGHT OUT A SET OF AIR STAIRS AND WE DEPLANED THE PAX THROUGH THE REAR ENTRY AND TRANSPORTED THEM TO THE TERMINAL VIA BUS. WE THEN WORKED WITH A MECH TO EVALUATE THE ACFT AND SEE WHAT WE COULD DO TO GET THE NOSEWHEEL BACK ON THE TXWY. HE EVALUATED THE ACFT AND SAID THE ACFT WAS UNDAMAGED. HE THEN PROCEEDED TO DIG OUT THE SNOW AROUND THE NOSEWHEEL SO WE COULD PULL THE ACFT OUT ONCE EQUIP ARRIVED. AFTER 6 HRS OF WORK INVOLVING SNOWPLOWS; A LARGE TOW TRUCK; AND ONE OF OUR TUGS; WE RODE THE BRAKES AND THE ACFT WAS TOWED TO THE RAMP BY OPS PERSONNEL. AFTER THE HVY SNOW STOPPED; WE BEGAN TO SEE OUR SURROUNDINGS MORE CLEARLY. WE REALIZED THAT TXWY XW HAD BEEN COVERED WITH HVY SNOW AS WE CROSSED IT AND AS A FURTHER COMPLICATION; 4 OF TXWY XW LIGHTS; ON THE N SIDE OF TXWY XW WERE IT INTERSECTS WITH TXWY XU; WERE NOT LIGHT AT ALL -- BUT RATHER UNLIT BLUE POLES. THIS COMBINATION OF NO EDGE LIGHTS ON THE N SIDE OF TXWY XW AND HVY SNOW MADE TXWY XW APPEAR NOT TO BE A TXWY IN THE HVY SNOW CONDITIONS. WHAT WE PERCEIVED TO BE THE TXWY XW LIGHTS WERE REALLY CARGO RAMP EDGE LIGHTS ON THE R (N) SIDE AND THE FEW REMAINING LIT TXWY XW LIGHTS ON THE L (S) SIDE. THE PERCEIVED ACFT TAXI TRACKS WERE TUFTS OF GRASS IN THE SNOW IN A RAISED AREA OF EARTH RUNNING PARALLEL TO TXWY XW. WE WERE FOOLED BY FALSE CUES THAT SHOWED US BOTH WHAT WE EXPECTED TO SEE. THE AMOUNT OF SNOW AT ZZZ MADE CORRECTLY IDENTING TXWY XW VERY DIFFICULT WITH AN ABSENCE OF RAISED LIGHTS ON THE N SIDE OF THE TXWY. IN HINDSIGHT; I WOULD COMPLETELY STOP THE ACFT AND ASK FOR THE ASSISTANCE OF A FOLLOW-ME OR A TUG TO THE GATE. SUPPLEMENTAL INFO FROM ACN 777494: I BEGAN DAY 3 OF A 4-DAY RESERVE BLOCK IN OUR DEP CITY. RERTES THE PRIOR DAY LED TO A 16 HR 32 MIN DUTY DAY WITH 9 HR 3 MIN REST. DESPITE THE LONG DAY AND SHORT REST PERIOD; I FELT ADEQUATELY RESTED FOR THE DAY AHEAD WHICH WAS TO BE 2 LEGS AND 2 DEADHEADS.

Data retrieved from NASA's ASRS site as of May 2009 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.