Gravel packing method for multilateral well prior to locating a junction

A lateral is gravel packed without a junction in place in a single trip into the wellbore. A disconnect is provided between the isolation packer in the lateral and a main bore packer. The inner string assembly in the gravel packing completion releases a disconnect with a shift tool and then releases the main bore packer so that the inner string assembly takes out the main bore packer and the upper portion of the disconnect when pulling out of the hole. A junction is then placed into the main and lateral legs with a packer having a seal bore into which the production string is sealingly stabbed to produce out of the main bore and/or the just completed lateral.