North American lumber prices are soaring to levels not seen in seven months as the lingering effects of flooding in Western Canada disrupt supplies and shipments.  Lumber futures jumped 3.8% to the exchange limit of $1,219 per 1,000 board feet in Chicago Thursday, touching the highest price since June 7. Prices have been climbing since rainstorms hit British Columbia in November, damaging highways and rail lines and forcing sawmills to temporarily shutter operations. Persistent supply logjams and strong demand are fueling the rally.  The surge adds to swelling homebuilding costs when ...