The top of the later weir is elevation 879. The ground surface on the Mesh is 875. The flow over the weir is controlled with a rating curve instead of the actual weir, therefore the weir is above what the highest flow would get to. HEC-RAS requires a weir to be in place to be able to use a rating curve for the lateral weir discharge. It is what places the RC on the cross-section and points it to the mesh.
I have run it with the weir set to the ground surface and do not get the results we need either. Hence the reason for the RC. The purpose of the RC is also to make sure the breach flows are right, as 33% of the flows go through this weir and not through the main dam structure, therefore reducing the breach flows during a PMF event. Where the problem comes in, is that it is giving me issue down stream of the weir where I am trying to get a floodplain of the weir flows. The watersurface elevation is increasing as the weir flow leaves the lake.