We head into the weekend facing not one, but two possible shocks to the economy.

There’s the fiscal cliff, of course. And then there’s the possibility of a port strike. Unionized longshoremen at 14 ports from Maine to Texas threaten to strike at midnight on Saturday, over a pay dispute.

A potential port strike is something to worry about, says Chris Low, chief economist at FTN Financial. “This is a big deal because the strike is so far reaching,” he says. It includes ports that collectively are responsible for about 40 percent of the country’s international trade.

Some retailers, like Walmart, will be relatively unaffected because they do most of their ordering in the months leading up to the Christmas season. Others won’t be so lucky.

“Companies like Home Depot and Lowes [will feel the strike], because their Christmas comes in April — the beginning of the homebuilding season. If the strike lingers long enough, they may find that their shelves are not stocked in time,” Low adds.