Citing supply chain sources, DigiTimes reports that Apple is expected to see only modest "single-digit" shipment growth for its notebook lineup in 2013, with the 13-inch MacBook Pro in particular seeing weaker-than-expected sales.Apple was confident about its 13-inch MacBook Pro performance for 2013, but the device's actual sales turn out to be weaker than expected, leaving the company still digesting its inventories in the first quarter. The sources pointed out that Apple's MacBook Pros have strong attraction to consumers, but the devices' high prices are instead pushing consumers away.The report also claims that Apple will be refreshing its notebook lineup "at the end of the second quarter", which could mean an introduction at the company's Worldwide Developers Conference expected in June.