Fast solar wind streams are known to be dominated by Alfvenic turbulence, i.e. large amplitude magnetic field and quasi-incompressible velocity fluctuations with a correlation corresponding to waves propagating away from the Sun. At the same time the Ulysses spacecraft showed That microstreams, persistent long period (1/2-2 days) fluctuations in the radial velocity field, are ubiquitous in the fast wind. This contribution explores the possible causal relation between microstreams and Alfvenic turbulence. We carry out a parametric study of the stability of the microstream jets to Kelvin-Helmholtz (KH) instabilities: starting from the profiles of density, radial speed and magnetic field observed in the solar wind, we investigate both at what distance from the Sun KH instabilities may be triggered and the ensuing nonlinear dynamics.