We present a new forecasting method for future CMB instruments, as well as an overview of the design and status of the Simons Array experiment. CMB4cast is a new code allowing the CMB community to estimate the scientific performance of a given instrumental design in the presence of astrophysical foregrounds and gravitational lensing. The Simons Array is a CMB polarimetry experiment which aims at characterizing the arcminute angular scale B-mode signal from weak gravitational lensing and search for the degree angular scale B-mode signal from inflationary gravitational waves. It is composed of three receivers observing at 95, 150, 220 and 280GHz, each of them having a 365 mm diameter focal plane cooled to 270 milli-Kelvin. The entire array has 22,764 polarization sensitive Transition Edge Sensor (TES) detectors, associated with lenslet-antenna coupled pixels that are sensitive to two frequency bands simultaneously. The first receiver, named Polarbear-2, will deploy in 2016 in the Atacama desert in Chile. The Simons Array will achieve first light in 2018 and will be able to constrain tensor-to-scalar ratio to σ(r = 0.1) = 6 × $10^{−3}$ , and the sum of neutrino masses to ($\sum m_v$)= 40 meV when combined with spectroscopic galaxy surveys.