  Let $W$ be a finite Weyl group and $\A$ be the corresponding Weyl
arrangement. A deformation of $\A$ is an affine arrangement which is obtained
by adding to each hyperplane $H\in\A$ several parallel translations of $H$ by
the positive root (and its integer multiples) perpendicular to $H$. We say that
a deformation is $W$-equivariant if the number of parallel hyperplanes of each
hyperplane $H\in \A$ depends only on the $W$-orbit of $H$. We prove that the
conings of the $W$-equivariant deformations are free arrangements under a
Shi-Catalan condition and give a formula for the number of chambers. This
generalizes Yoshinaga's theorem conjectured by Edelman-Reiner.
