U.S. corn futures are expected to take direction from external markets Friday as traders remain on edge after the plunge in commodity and equity markets Thursday.

Traders predict corn for December delivery, the most actively traded contract, will start 2 cents to 5 cents a bushel lower at the Chicago Board of Trade after dropping 7 1/2 cents, or 1.1%, to $6.94 a bushel in overnight trading. They pared back predictions for losses as the better-than-expected jobs report helped stabilize crude oil prices and push up stock futures.

Traders are keeping their eyes on the external markets after grain prices tumbled Thursday amid widespread selling sparked by concerns about the global economy. Fears have intensified recently about the risks of U.S. economy faltering and the euro zone's debt crisis spreading, fueling the biggest selloff in U.S. stocks in two years Thursday and dragging down commodity markets.

"The ability of the outside markets to find support and rally could signal the grain markets to also find support," said Brian Hoops, president of Midwest Market Solutions, a commodities brokerage in South Dakota.

Volatility has been high in the corn market for months due to nervousness about historically tight inventories. Corn prices reached an all-time high in early June and have since pulled back 14%.

Friday's job report appeared to temporarily calm some nerves about the economy. Grain futures could start trading slightly higher when the markets open at 10:30 a.m. EDT if crude oil and copper prices are stronger, said Mike Zuzolo, president of Global Commodity Analytics & Consulting, a brokerage in Indiana.

For many others, uncertainty about the economy continues to hang over the grains. Traders may continue to take profits heading into the weekend, as the December corn contract was still up 32 3/4 cents for the week as of Thursday's close of trading, analysts said.

Market participants also are cautious ahead of highly anticipated U.S. Department of Agriculture crop reports next week. They worry the department may project a larger harvest than has been reflected in recent private estimates.

Still, Barclays Capital said it remained positive on corn prices due to concerns about intense July heat reducing output. Poor weather is worrisome as farmers need to harvest a large crop to replenish low supplies. Weather forecasts in August "look more benign, with expectations of cooler weather keeping external markets and macro-factors in the driving seat," according to Barclays.