The surface elevation field over a shelf-slope region is subject to a parabolic differential equation, the timelike coordinate being longshore distance in the direction of propagation of vorticity waves. Two source terms in this equation contain long-isobath and cross-isobath density gradients. In the absence of long-isobath variations the particular solution of the equation containing the cross-isobath density gradient source term describes a steric setup distribution, which represents a plausible extension of the dynamic height method to shallow water. When long-isobath variations of density are also present, the steric setup solution is complemented by a residual field, which is essentially a diffusive smoothing out of the steric setup distribution. The steric setup distribution calculated for the shelf-slope region of the Northwest Atlantic from Cape Hatteras to the Grand Banks shows two major features: a mound of water associated with the St. Lawrence outflow and a rapid drop at the shelf break associated with an upper slope mean current having a surface velocity of the order of 20 cm s-1. The effects of the St. Lawrence outflow are felt mainly over the Scotian Shelf and in the Gulf of Maine. The shelf break current is apparently a boundary layer component of the cyclonic gyre between the Gulf Stream and the North American mainland.