Apple Inc. delivered a surprisingly strong revenue forecast for the third quarter, even as it warned that memory-chip costs will increase and that shortages of Mac computers will persist for “several months.”

Sales will rise 14% to 17% in the period, which runs through June, the company said during a post-earnings conference call Thursday. That range trounced the 9.1% that analysts had anticipated on average, helping send the shares rallying in New York on Friday.