Massive flooding late last year that washed away rail tracks and shut highways in Western Canada forced one of the nation’s biggest lumber producers to curtail output.  West Fraser Timber Co. said in a statement that while repairs to rail and truck routes in British Columbia are progressing, its ability to “ship products in a timely manner remains challenged.” The company said it was forced to take “unscheduled downtime” due to the transportation constraints.  The cutback in production from a major supplier threatens to further boost lumber futures that have already risen 32 ...