Athletic footwear and apparel maker Under Armour’s plan to build a 1.3-million-square-foot e-commerce distribution and warehouse facility is set to boost container traffic through the nearby Port of Baltimore and enhance the larger logistics park it will move goods through.

Prospects for East Coast ports are brightening, especially on the export side, as the global economic recovery fuels demand for everything from automobiles to grain and forest products. But a number of variables could disrupt the ports’ projections, on the upside and the downside.

The Port of Baltimore’s Seagirt and Dundalk public marine terminals will be open Saturday for the delivery and receipt of cargo if no agreement is reached...