Lift Pressure Distribution
The key to the lift generation is the curvature of the streamlines. Forget the popular, but unfortunately wrong explanations based on the non-equidistant particle paths.
The simplest example will be if you place a plate with an angle of attack in the subsonic flow: the streamlines will get curved on the both plate sides as the flow turns.
Therefore, even a flat plate will generate a lift once its angle of attack is different from zero. As the streamlines are turning on the upper surface, the pressure will get reduced from the free-stream to the airfoil surface.
In other words, moving away from the airfoil, the pressure will increase - in the direction of the radius of curvature of the streamlines.
Important to note is, that this pressure drop is normal to the streamlines. This change in pressure is simply an effect of turning the flow, i.e. changing its direction.
Mathematically, the pressure gradient normal to the streamline, dp/dn, can be expressed as
$$ \frac{dp}{dn} = \rho \times \frac{V^2}{R} , $$
where R is the radius of curvature the streamline. Derivation of this equation can be obtained if writing the momentum equations in the natural coordinates.