Canadian National Energy Board (NEB) data released earlier this month shows that the flow of natural gas imports across the US border at Niagara reversed to become exports for the first time in 2012. In the “old world” before Marcellus in 2008 - Canadian gas flowed into the US at an average 0.9 Bcf/d at Niagara. Last year those imports ground to a halt from May to October 2012 before reversing to 0.3 Bcf/d of exports to Canada in November. The reversal confirms that expanding Marcellus supplies are not just pushing Canadian imports back over the border but also starting to penetrate the Canadian market. Today we look at the dynamics of the Northeast gas flow reversal.