ACR MLG MAKE A TKOF ON A CLOSED RWY.

Narrative

THIS SCHEDULED FLT DEPARTS BEFORE TWR OPENS. ATIS WAS NOT MONITORED AS TWR CLOSED FOR OVER 6 HRS. WX PRIOR TO LEAVING OPS; 30 MINS PRIOR DID NOT NOTE ANY NOTAMS. PAPER COPY OF WX WAS RECEIVED SEVERAL MINS BEFORE RAMP DEP AND WAS REVIEWED FOR DEST WX AND FORECASTS. LCL WX HAD GOOD VISIBILITY AND ALL RWY AND TAXIWAY AREAS WERE CLRLY IN VIEW. WE ADVISED ON TWR FREQ WHEN WE DEPARTED ON RWY 27. DURING THE INTERIM WE CALLED FOR AND RECEIVED IFR CLRNC FROM CHICAGO ATC FOR OUR FLT TO MKE. WE HELD SHORT OF RWY 27 UNTIL WE COMPLETED OUR TKOF CHKS. WE NOTED AN ARPT VEHICLE ALSO HOLDING SHORT OF THE RWY ACROSS THE RWY FROM US; WHICH WE ASSUMED WAS WAITING FOR OUR DEP. AFTER TAXIING INTO POS WE NOTED A SNOW REMOVAL VEHICLE MOVE CLR OF THE RWY ON THE FAR END. WHEN IT APPEARED THAT THE VEHICLE WAS HOLDING CLR OF THE RWY; WE TOOK OFF. THE RWY WAS WELL CLRED OF SNOW AND APPEARED FULLY OPERATIONAL -- THE RWY LIGHTS BEING ON. IN RWY AND TAXI LIGHTS ON RAMP DEP. AT NO TIME DID WE HEAR ANY RESPONSE TO OUR CALLS. SEVERAL HRS LATER WE WERE INFORMED THAT THE RWY HAD BEEN NOTAMED CLOSED THE PREVIOUS NIGHT. WE WERE TOLD THAT HAD WE CHKED THE ATIS WE WOULD HAVE BEEN AWARE OF THE CLOSED RWY. EVEN SO; WE MIGHT HAVE ASSUMED THAT TO BE OUTDATED INFO AS THE RWY HAD BEEN CLRED. THE SAME ASSUMPTION MAY HAVE BEEN MADE IN REGARD TO THE NOTAM RPT. NOR DID THE COMPANY RAMP PERSONNEL MENTION THE CLOSED RWY TO US. I WOULD SUGGEST THAT THE RWY LIGHTS BE OFF IF A RWY IS CLOSED.