This airframe has a history of NWS problems as proved problematic at MAN a little while ago. The crew vacated the runway onto the parallel taxiway by making two left 90 degree turns to go to the terminal. Unfortunately directional control was lost during the second turn and the aircraft continued to turn left onto the grass. Any available braking was greatly reduced by snow/ice towards the taxiway edges. A probable NWS or BSCU fault is being investigated. They were very unlucky to get that just as they were turning... There but for the grace of God go the rest of us....