This work extends the existing WRF-IBM model to implement appropriate flux boundary conditions based on Monin-Obukhov (M-O) similarity theory. Three different surface treatments are implemented at the immersed boundary, to develop an IB method which enforces M-O theory for atmospheric boundary layer applications. The surface treatments used in this work are all known as direct forcing, first used in the work of Mohd-Yusof (1997). With this method, the velocity or the shear stress value is modified at the points near the boundary to enforce the correct boundary condition. The first method is a ghost cell IBM method, where velocity is reconstructed at the ghost cell below the surface based on M-O similarity theory. The second method is also a ghost cell method, but instead of reconstructing velocity at the ghost cell, the shear stress is reconstructed. The third method is based on velocity reconstruction as in Fadlun et al , where the velocity is reconstructed at the first fluid node according to the logarithmic profile. Validation test cases include pressure driven flow over flat terrain and an idealized valley with a neutral atmospheric boundary layer. The simulations will be used to evaluate the performance of the different surface treatments in WRF-IBM over complex terrain.