Bay Street is poised for a positive open on Tuesday, supported by higher Canadian and U.S. futures and firm commodity prices, though U.S. President Donald Trump's decision to impose additional 50% tariffs on a wide range of goods imported from Canada may weigh on sentiment. Trump signed three Proclamations under Section 338 of the Tariff Act of 1930 on Monday, citing retaliation for what he called Canada's discriminatory treatment of American products such as cars, dairy and alcohol. On Monday, the S&P/TSX Composite Index fell 303.53 points, or 0.86%, to close at 34,960.32. In commodities, West Texas Intermediate crude oil futures rose $1.10, or 1.3%, to $84.33 a barrel, while gold futures gained $47.00, or 1.18%, to $4,062.90 an ounce.