Chicago Board of Trade corn futures are expected to open weaker Friday thanks to outside market pressure and drier weather expected next week.

Corn is called 3 to 5 cents lower. In overnight trade, December corn was down 4 3/4 cents to $3.74 3/4 per bushel and March corn was down 4 1/4 cents to $3.88 1/4.

The market remains largely at the mercy of outside macro markets, particularly the U.S. dollar, which appears firm and could weigh on prices Friday, traders said. Lower crude oil could add to the pressure, they said.

The market is vulnerable to a setback after climbing more than 10 cents Thursday, a trader said.

Traders are also keeping an eye on the weather. Drier weather is expected starting this weekend, first in the western corn belt and then into eastern areas next week. That should help farmers pick up the harvest pace, analysts said.

But the duration of the dry period will be important, they said.

"We definitely need to hold this dry window open," a trader said.

Currently much of the U.S. corn belt is being soaked by constant rains, and parts of the heart of the region have seen several inches the past couple weeks. That means farmers won't be able to harvest right away, said Mike Zuzolo, president of Global Commodity Analytics and Consulting.

"This dry weather spell that's coming out, we may only see half of that used by the producers to get out and shell corn," Zuzolo said.

Traders and analysts note that demand for corn, other than for ethanol, has been weak recently. Low weekly export sales reported Thursday reaffirmed that the market priced itself out of demand on its recent rally, they said.

Bulls' next upside price objective is to push and close prices above solid technical resistance at $3.88 3/4 a bushel, a technical analyst said. The next downside price objective for the bears is to push and close prices below solid technical support at this week's low of $3.63 3/4 a bushel.

First resistance for December corn is seen at Thursday's high of $3.81 3/4 and then at $3.85. First support is seen at $3.75 and then at $3.70.

So far this week, December corn is down 18 1/4 cents.

-By Ian Berry, Dow Jones Newswires; 312-341-5778; ian.berry@dowjones.com