Apple 15-inch MacBook Pro shipment estimates fluctuate, drop to 1-2 weeks ahead of WWDC

As of Wednesday, Apple's online storefront shows the largest MacBook Pro model with integrated Intel graphics as shipping in one business day, while availability of the step-up model with discrete Nvidia GPU is currently at one to two weeks.

The 15-inch MacBook Pro was noticeably passed over when nearly every MacBook model received modest refreshes last month. Both MacBook Air versions were updated with Intel's latest Broadwell processors and Thunderbolt 2 connectivity, while the 13-inch MacBook Pro with Retina display also got a CPU boost, alongside Force Touch trackpads and other under-the-hood improvements last month.

At the time, production of performance-class Broadwell chips expected for inclusion in a refreshed 15-inch MacBook Pro was delayed.

In addition to Apple's own stock on hand, authorized resellers have also seen recent erratic shifts in supply, said a source familiar with the matter. Apple slowly drew down channel shipments during the March to April period, but just recently sent out a fresh batch, the person said.

One theory that could account for low supply of 15-inch models with discrete GPUs is a recent foundry shift by Nvidia, Apple's sole supplier of dedicated MacBook Pro graphics cards. However, Nvidia likely forecast a dip in output and adjusted accordingly.

With fluctuations in both direct sales and reseller channels, however, Apple could be clearing the way for a new model set to debut at the Worldwide Developers Conference in June. The laptop is expected to come with modest CPU speed enhancements, buffed SSD performance and Apple's new Force Touch trackpad.

Apple's 15-inch MacBook Pro with Retina display was last updated in July 2014 with Haswell CPUs and a doubling of standard RAM allotments.