I'm trying to determine the pressure on a surface where the length is short enough that the velocity should be constant across it.

Fan -> -8_________________
                ^-- surface

So, the idea is that there is air forced over the top of the surface and the air below it is not moving. How do I calculate this?

I've seen this equation: $$ P_1 + {1 \over 2} \rho v_1^2 + \rho g y_1 = P_2 + {1 \over 2} \rho v_2^2 + \rho g y_2 $$ where: $P$ is the pressure of the fluid, $\rho$ is the fluid density, $g$ is the local gravitational acceleration, $v$ is the fluid's speed and $y$ is the height of the fluid, which seems to be what I am looking for, but I'm not sure what height relates to.